AlgebraStructure & Method · Book 1All Chapters

Transforming Equations

3-1Transforming Equations: Addition and Subtraction

Overview

Add or subtract the same number from both sides to isolate the variable.

Key ideas

  • Whatever you do to one side, do to the other.
  • Aim to get the variable alone.
  • Always check by substitution.

Worked examples

Example 1

Problem. Solve x − 7 = 12.

Solution. Add 7: x = 19.

Example 2

Problem. Solve y + 5 = 2.

Solution. Subtract 5: y = −3.

Practice

Try each one. Click Show answer when ready.

  1. 1.

    Solve a + 8 = 3.

  2. 2.

    Solve m − 4 = 11.

  3. 3.

    Solve x + 12 = 0.

Challenge problems

A little tougher — great for test prep. Click Show answer when ready.

  1. 1.

    Solve: x − 7 = −12. Check your answer.

  2. 2.

    Solve: −3 = y + 8. Check your answer.