Algebra practice question

Answer: 3

Expand the right side: 6x + 3b. For 6x + 9 = 6x + 3b to hold for every x, the constants must match: 3b = 9, so b = 3.

Common wrong answers

If you answered 0

0 would give 6x + 9 = 6x, which is never true.

If you answered 6

6 is the coefficient of x, not b.

If you answered 9

9 is 3b, one step short; the 3 outside the parentheses multiplies b.

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