Algebra practice question

Answer: 6

−9 ≤ 3x − 6 ≤ 9 gives −3 ≤ 3x ≤ 15, so −1 ≤ x ≤ 5: an interval of length 6.

Common wrong answers

If you answered 4

4 pairs the endpoints 1 and 5, dropping the sign of −1.

If you answered 5

5 is the right endpoint, not the length.

If you answered 18

18 is the length before dividing by 3.

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