Illustrate with an example that (a + b) - c = a + (b - c) in the set of whole numbers
Pick any a, b, anc c that you like and perform the operations in the indicated order, with the parentheses first. See if it works.
For example try a= 4, b = 2, c = 5
(4+2)- 5 = 6 - 5 = 1
4 + (2-5) = 4 - 3 = 1
It works.