The correct answer is (B).
Getting to the Answer: First subtract 7 from both sides to get 3x = 15. Then divide both sides by 3 to get x = 5. The question asks for the value of 2x, so multiply x by 2 to obtain 2(5) = 10.
(A) Incorrect: this is the value of x, not 2x
(B) Correct: this matches the correct calculation
(C) Incorrect: this is the result of subtracting 3 from 15 rather than dividing by 3
(D) Incorrect: this is the result of reasoning that 2x is 1 less than 3x = 15
(E) Incorrect: this is the result of adding 7 to the right side rather than subtracting 7
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