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If 3x + 12 = 21, then x + 4 = A. 3 B. 4 C. 5 D. 7 E. 9

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by Brent@GMATPrepNow » Mon Dec 17, 2018 6:38 am
BTGmoderatorDC wrote:If 3x + 12 = 21, then x + 4 =

A. 3
B. 4
C. 5
D. 7
E. 9
One option is to first solve the equation, 3x + 12 = 21, for x, and then determine the value of x+4.

Alternatively, we can factor the left side to get: 3(x + 4) = 21
Now divide both sides by 3 to get: x + 4 = 7

Answer: D

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by Scott@TargetTestPrep » Thu Mar 14, 2019 5:59 am
BTGmoderatorDC wrote:If 3x + 12 = 21, then x + 4 =

A. 3
B. 4
C. 5
D. 7
E. 9

OA D

Source: Princeton Review
Dividing the given equation by 3, we have:

x + 4 = 7

Answer: D

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Founder and CEO
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