All of the following are equivalent, except a)2x + x b)x(2 + 1) c)2x² d)3x

C) 2x^2

Explanation:
The easiest way is to evaluate all the given choices and then pick the odd one.
First choice:
2x + x = 3x > I
Second choice:
x(2+1) = 2x + x = 3x > II
Third choice:
2x^2 > III
Fourth choice:
3x > IV

From the above, we can note that:
Expressions I,II and IV are equal whereas III is the odd one
Besides, the third choice is a the only one that is has x^2

Therefore, the third choice is not equivalent to the others

Hope this helps :)