Question

verify a(b x c) =(a x b) x c = 5

Answer 1

on solving first part, we get
abc =abc=5
it means abc=5 .
VERIFIED !!!

Answer 2

a(b*c)=a(bc)=abc
(a*b)*c=(ab)c=abc
but it's not necessary that they are equal to 5.
It can be only proved when the values of a, b, c are given.