Hey Aspirant!

A binary operation ∗ on A is associative if  ∀a,b,c∈A,

(a∗b)∗c=a∗(b∗c) and

A binary operation ∗ on A is commutative if  ∀a,b∈A,

a∗b=b∗a

a∗b=4=a+b/4 is commutative as:

a∗b=b∗a

⇒a+b/4=b+a/4

⇒a+b/4=a+b/4

which is true.

a∗b=a+b/4 is not associative as:

(a∗b)∗c=a∗(b∗c)

⇒(a+b/4)∗c=a∗(b+c/4)

⇒(a+b/4)+c/4=a+(b+c/4)/4

⇒(a+b+4c)/16= (4a+b+c)/16

which is not true.

Hence, the binary operation ∗ is commutative

Hope this will help you

All the Best