Question

Which of the following terms are like terms?
 a) 9x and 9y b)12ac^2 and ac^2 c)8xy and 8xz d)ab^2 and x^2y

Answer 1

Like terms means terms that have the same variable (and with the same exponent). 

A) 9x and 9y <-- those are different variables. This is incorrect.

B) 12ac^2 and ac^2 <-- those are the same variables and same exponent. Correct.

C) 8xy and 8xz <-- different variables, incorrect.

D) ab^2 and x^2y <-- different variables, incorrect.

Correct answer is $\fbox {B)}$

Answer 2

Like terms are terms that have the same variables and also have the same exponents on those variables.

Out of all your choices, answer choice B) 12ac^2 and ac^2 fits that definition.

B is your answer.