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

To find the missing step in the proof of the equivalence of \( 12a + 10 + a = 10 + a + 12a \), we can identify the appropriate expression that uses the Commutative Property.

The Commutative Property states that the order in which two numbers are added does not change the sum. Therefore, we can rearrange the terms.

The first step can be to rearrange the terms on the left side of the equation:

**Step 1**: \( 12a + a + 10 = 10 + a + 12a \)

Now, when we combine \( 12a + a \) on the left side, we have:

**Step 2**: \( 10 + 13a = 10 + 13a \)

Thus, the missing step in proving the equivalence is:

**Response**: \( 12a + a + 10 = 10 + a + 12a \)