Undo Buttons

Inverse operations, in reverse order

An interactive lesson with 9 steps, about 8 minutes: you predict, drag and solve, with instant feedback on every answer. It runs in your browser and needs JavaScript.

What you’ll learn

• Addition and subtraction undo each other, and so do multiplication and division.
• Undo operations in reverse order: the last thing done to $x$ is the first thing you undo.
• A number in front of brackets multiplies everything inside: $2(x+4) = 2x+8$.
• Always check by putting your answer back into the original equation.

Steps

1. Think of a number
2. Every operation has an undo button
3. The right undo
4. Solving in order
5. Your turn
6. Below zero
7. Spot the mistake
8. Fix it
9. Taxi ride