Answer:
Step-by-step explanation:
From the left hand side,
Let b*c = P, and c*b = P'
Then a*(b*c) = a*P
Because * is commutative,
b*c = c*b
a*P = P*a
a*P' = P' *a
are all true
So P = P'
a*P = a*P' (Since P = P')
a*P = P' *a (Since a*P' = P' *a)
a*(b*c) = (c*b)*a
For all a, b, c in S