If 3x + 7 = 25, what is the value of 6x + 4?
- A36
- B38
- C40
- D42
- E46
Practice bank · Quant
Solve a one-step linear equation cleanly
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Correct answer: C
Solve for x first. Subtract 7 from both sides: 3x = 18, so x = 6.
Now evaluate what was actually asked: 6x + 4 = 6(6) + 4 = 36 + 4 = 40.
Notice the question does not ask for x. Answer (B) is 3x + 7 evaluated at the wrong step, and 6 itself is not among the traps by accident: many test-takers solve for x, see 6, and grab whatever choice matches their scratch work. On both the GMAT and the GRE, the final line of your work should restate the question: “they want 6x + 4.”
A faster variant: once you know 3x = 18, double it to get 6x = 36, then add 4. You never need x explicitly.