Verona is solving the equation -3 + 4x = 9. In order to isolate the variable term using the addition property of equality, which number should she add to both sides of the equation?

To isolate the variable term 4x, undo the subtraction of 3 by adding 3 to both sides: −3 + 4x + 3 = 9 + 3. The −3 and +3 cancel on the left, leaving 4x = 12. So she should add 3, choice B.

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