algebra · Year 7 · Suggested learning sequence
Two-step equations
A two-step equation like 3x + 5 = 20 does two things to x: it multiplies by 3, then adds 5. To solve it, undo those steps in reverse order. First subtract 5 from both sides: 3x = 15. Then divide both sides by 3: x = 5. Check by substituting: 3 × 5 + 5 = 20. ✓ The order matters — take the added number off first, then divide. Stopping after the subtraction (giving 15) or dividing before subtracting are the two most common mistakes.
Sample questions
2x + 2 = 16. What is x?
- Subtract 2 from both sides: 2x = 16 − 2 = 14.
- Divide both sides by 2: x = 14 ÷ 2 = 7.
Answer: 7
2x + 4 = 10. What is x?
- Subtract 4 from both sides: 2x = 10 − 4 = 6.
- Divide both sides by 2: x = 6 ÷ 2 = 3.
Answer: 3
3x + 3 = 15. What is x?
- Subtract 3 from both sides: 3x = 15 − 3 = 12.
- Divide both sides by 3: x = 12 ÷ 3 = 4.
Answer: 4