Your Answer is

Correct Answer is B

Explanation

Analysis 1: Substitute 3, 5, 8, and 15 into the original formula, only 5 can make the equation true, choose B.

Analysis 2: The formula can be transformed into

3-x = 12-2x, and the solution is x₁ = 9

x -3 = 12-2x, the solution is x₂ = 5

But you need to pay attention to the positive and negative values, 12-2x ≥ 0, so x = 5