To determine the missing step using the Commutative Property, we need to rearrange the terms in the expression \(12a + 10 + a\).
The missing step is:
Step 1: \(10 + 12a + a = 10 + a + 12a\)
So the correct response is:
10 + 12a + a = 10 + a + 12a
This step uses the Commutative Property to arrange the terms in a new order.