How many of the students correctly applied only the associative property to rewrite the expression

Only one student, Melinda used it right.

Step-by-step explanation:

Associative property lets us place our brackets the way we want and the result would be unchanged.

Here: (13 + 15 + 20) + (20 + 47 + 18).

So, we can place the brackets in any form, like (13 + 15) + (20 + 20) + (47 + 18).

There are many ways to do it. Melinda's was is yet another example.

Note that Associative property does not hold for subtraction.

boxplot e is the answer