Algebra practice question

Answer: 17

Distribute the 3 first: 3x − 12 = 2x + 5. Subtract 2x from both sides: x − 12 = 5. Add 12: x = 17. Check: 3(17 − 4) = 3(13) = 39, and 2(17) + 5 = 39.

Common wrong answers

If you answered 7

7 is 12 − 5, the constants subtracted the wrong way round. After x − 12 = 5, adding 12 to both sides gives 17.

If you answered 9

That comes from 3x − 4 = 2x + 5 — the 3 was applied to x but not to the −4. Distributing means multiplying EVERY term inside the bracket: 3(x − 4) = 3x − 12.

If you answered −7

A sign slipped when the constants were collected: from 3x − 12 = 2x + 5, moving −12 across gives x = 5 + 12, not 5 − 12.

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