To complete the proof using the Commutative Property, we want to rearrange the terms in the expression \(12a + 10 + a\) so that it matches the order in the expression \(10 + a + 12a\).
The correct missing step is:
Step 1: \(12a + a + 10 = 10 + a + 12a\)
This rearrangement applies the Commutative Property, which states that the order of addition does not affect the sum.
So the complete sequence would be:
Step 1: \(12a + a + 10 = 10 + a + 12a\)
Step 2: \(10 + 13a = 10 + 13a\)
Step 3: The expressions are equivalent because they both equal the same value.