Question

Show that (A − B) − C is not necessarily equal to A − (B − C).

Answer 1

(3-2)-1=0

3-(2-1)=2

Boom! Done

Answer 2

(A-B)-C = A-B-C

A-(B-C) = A-B+C

You can see, 1rst & 2nd equations are not equal after simplification.