Authentic Lessons for 21st Century Learning

Going Viral

Solving Equations

Mariah Warren | Published: May 26th, 2022 by K20 Center

  • Grade Level Grade Level 7th, 8th, 9th
  • Subject Subject Mathematics
  • Course Course Algebra 1, Middle School Mathematics, Pre-Algebra
  • Time Frame Time Frame 1-2 class period(s)
  • Duration More 90 minutes


This lesson focuses on teaching students how to solve algebraic equations using student-friendly language. Students will try to solve viral math posts in groups. Then, they learn the Do/Undo method, practice with sample problems, and evaluate how viral math posts can be written and solved. Students then create their own viral math posts, and solve their classmates' equations. This lesson includes optional modifications for distance learning. Resources for use in Google Classroom are included.

Essential Question(s)

How can you represent, compare, and order numbers to solve an equation?



Students examine a four-square diagram and determine on their own which of four pictures doesn’t belong with the rest. Then, using the Four Corners strategy, students convince their peers to join their side. Then, groups review their choices and discuss how like things can be grouped.


In groups of six, students form strategies for solving viral math posts and peer-review their group mates' answers.


Students view a demonstration of the Do/Undo method for solving equations and practice solving sample problems.


Students generate their own algebraic equations and display them as viral math posts.


Using the Gallery Walk strategy, students view and solve other students' viral posts.


  • Going Viral Lesson Slides (attached)

  • Four Corners Signs (attached)

  • Pass the Problem handouts (attached; one set of handouts for every group of six students)

  • Gallery Walk handout (attached)

  • Sample Problems (attached)

  • Sticky easel pad paper

  • Markers (Mr. Sketch, Sharpie, etc.)

  • Colored pencils

  • Pens/pencils

  • Internet-connected devices for students (optional)


Introduce the lesson using the attached Lesson Slides. Slide two displays the lesson's Essential Question: How can you represent, compare, and order numbers to solve an equation? Slide three identifies the lesson's learning objectives. Review each of these with your class to the extent you feel necessary.

Go to slide four. Ask students to consider which item pictured does not match the others and why. Use the Four Corners strategy by instructing students to go to the corner with the name of the item they do not believe fits with the rest. Invite each group to discuss among themselves how to convince others to join their group. Allow 1–2 minutes for this discussion, then have each corner select a spokesperson to share out their reasoning. Allow others to change corners.


Go to slide five and introduce the Pass the Problem activity. Pair students into partners and then into larger groups, with three sets of partners per group. Pass out the attached sets of Pass the Problem handouts to each group. The handout contains three problems, one for each pair within a group to circulate. Inform the students they will attempt to solve these viral math posts. Each partner set within a group will start with a different viral post and solve it using the Pass the Problem strategy, as instructed on slide five. Give students 2–3 minutes to solve only the first line of the handout.

When time is up, direct students to pass the problem to another pair in their group. The new pair should check the first pair’s work on the first line, make any necessary corrections, and then solve only the second line. Give students 3–4 minutes to complete this round.

When time is up for the second round, direct the student to pass the problem to the pair that hasn’t worked on that viral post yet. This pair should check the first and second pair's work on the first and second lines, make any necessary corrections, and then solve only the third line. Give students 4–5 minutes to work this round.

Finally, direct students to return the viral post to the original pair that started it. This pair should check all of the work on the handout and solve the final line.

After the groups have completed their handouts, go through slides 6–8 to review the answers to each part of the problem.


Use slides 9-19 to demonstrate the "Do/Undo" method for solving equations. You can use this video on slide nine (the full URL can also be found in Resources below) to demonstrate the method, or see below for instructions and sample problems. Slides 10, 12, 14, 16, and 18 are hidden and show the method for solving the problems on the previous slide. You may choose to unhide these solution slides as you go over the problems. Introduce the terms coefficient, constant, and variable as you work these problems with the students.

Solving Equations with Undo Tables

Right side: Setting up a Do/Undo table. Left side: Solving an equation by completing the table. The answer, circled, is mirrored opposite the variable.
  1. Begin by combining like terms and introducing a variable.

  2. Isolate the variable you are solving for.

  3. List in steps what is happening to the variable, using order of operations. In the below example, x is first multiplied by four, then added to by five, which is taken to equal 25.

  4. Mirror the bottom-most value (25, in the above example) by copying it to the bottom row to the right of the T.

  5. Working from the bottom to the top on the right side of the T, write the operation opposite to the one on the right. In the above example, +5 is opposite of -5, and /4 is opposite of *4.

  6. Using the bottom-most number, perform each operation, working up. Write your final number on the top-right of the T, mirroring the variable. To check your answer, plug it into the variable in the starting position and perform the operations below, from top to bottom. If it then equals the number on the bottom-left, you've confirmed the answer is correct.

Move to slide 20. Select problems from the attached Sample Problems for students to work on using the Do/Undo method. You may do as many of these problems with your students as you see fit.


Go to slide 21. Invite students to generate their own algebraic expressions and display them as a viral math post, similar to the ones they solved on the Pass the Problem handout. To do so, have them follow the directions on the slide:

  • Ask students how these viral posts are designed to trick people (e.g., the order of operations, distracting lines, etc.)

  • Have students begin by deciding on their variables (e.g., pictures, emojis, etc.)

  • Students should have at least four lines and three variables included in their viral math post.

  • Students must also create a separate answer key for their problem.

Once students have completed and checked their rough drafts, invite them to create a poster for their final draft.


Go to slide 22 and pass out the attached Gallery Walk handout to each student. Have the class display their final drafts around the room and conduct a Gallery Walk. Ask each student to solve the math posts of five other students, using their handouts. After students have solved five posts, ask each student to present the answer key for their viral math post in order for everyone to check their work.