Worked examples
Two examples
Example 1
Solve: x + 7 = 12
- Undo adding 7 by subtracting 7 on both sides: x = 12 − 7.
- Check: 5 + 7 = 12.
Answer: x = 5
Example 2
Solve: x − 4 = −9
- Undo subtracting 4 by adding 4 on both sides: x = −9 + 4.
- Check: −5 − 4 = −9.
Answer: x = −5
Where this is taught: Algebra Practice 1, “13. Adding and subtracting”
The drill
Ten problems
How many:
Type each answer, then press Check my answers at the bottom. Commas in large numbers are fine.Write each answer on the line. The answer key, with the reasoning, is on the last page.