Associative law is not applicable to subtraction and division, change of grouping of numbers, changes the results.
For example, 3 – (4 – 5) and (3 – 4) – 5 are not equal, since,
3 – (4 – 5) = 3 – (-1) = 3 + 1 = 4
(3 – 4) – 5 = (-1) – 5 = -1 – 5 = -6
Thus, 4 ≠ -6