Use the Commutative Property to determine the missing step in proving the equivalence of 12a+10+a=10+a+12a .

To determine the missing step in the proof of equivalence between \( 12a + 10 + a \) and \( 10 + a + 12a \) using the Commutative Property, we need to show how we can rearrange the terms.

The expression \( 12a + 10 + a \) can be rearranged as follows:

1. **Step 1: 10 + 12a + a = 10 + a + 12a**

This rearrangement is valid by the Commutative Property, which states that the order of the terms can be changed in addition.

Now we can conclude:

- **Step 2:** The equation can also be written as \( 10 + 13a = 10 + 13a \) through combining like terms \( 12a + a = 13a \).

- **Step 3:** Finally, since both expressions evaluate to the same form, we can state they are equivalent.

Therefore, the correct response for the missing step is:

**10 + 12a + a = 10 + a + 12a**