All of the following are equivalent, except.

(12+3) x

(12+3x) x

15x

12x+3x

Answer: (12+3x) x

Explanation: When you distribute the x in the first option you'll get 12x+3x, which you can simplify to 15x (combine like-terms). Having this information, you know that the first one is equivalent to the third one and the fourth option. When you distribute the x in the second you you get (3x^2) + 12x. This is not equal to any other option.