Bunuel wrote:

GMAT CLUB TESTS' FRESH QUESTION.

What is the value of |m| - |n|?

(1) n^2 = 36

(2) m^2 = 81

(1) n^2 = 36n = 6 or -6

No info about m

Insufficient

(2) m^2 = 81m = 9 or -9

No info about m

Insufficient

Combine both 1 & 2

In any value of n & m, then |m| - |n| will have fixed value. Let's see:

Let n =6 & m = 9....|m| - |n| = |9| - |6| = 3

Let n =6 & m = -9....|m| - |n| = |-9| - |6| = 3

Let n =-6 & m = 9....|m| - |n| = |9| - |-6| = 3

Let n =-6 & m = -9....|m| - |n| = |-9| - |-6| = 3

Sufficient

Answer: C