Help? Step 2 and 3, for step 2, Associative property should be Commutative property, and step 3 should be Associative property instead of the Commutative property, I did all the work and its right, but how should I explain it?

Help Step 2 and 3 for step 2 Associative property should be Commutative property and step 3 should be Associative property instead of the Commutative property I class=