16Hit1600
AlgebraHardNumber from a half of a difference

Algebra practice question

Half of the difference between three times a number and 4 is 25. What is the number?

Answer: 18

(3n − 4)/2 = 25 gives 3n − 4 = 50, so n = 18.

Common wrong answers

If you answered 27
27 solves 3n/2 − 4 = 25, halving only the 3n.
If you answered 50
50 is 3n − 4.
If you answered 15.33
15.33 solves 3n − 4 = 25 without doubling.

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