Algebra practice question

Answer: 13

From the second, x = 9 − 2y. Substitute: 18 − 4y − 3y = 4, so 7y = 14, y = 2, x = 5. Then 3x − y = 15 − 2 = 13.

Common wrong answers

If you answered 5

5 is x alone.

If you answered 7

7 is x + y.

If you answered 17

17 is 3x + y, adding instead of subtracting.

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