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 proving the equivalence of \( 12a+10+a=10+a+12a \) using the Commutative Property, we can rearrange the terms appropriately.

Let's break it down:

The goal is to express \( 12a + 10 + a \) in a way that highlights its equivalence to \( 10 + a + 12a \).

In Step 1, we can rearrange the terms:

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

This matches the structure leading to Step 2. From Step 1, we can combine like terms (the \( 12a + a = 13a \)), giving us:

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

Thus, the complete sequence is:

- Step 1: \( 10 + 12a + a = 10 + a + 12a \)
- Step 2: \( 10 + 13a = 10 + 13a \)
- Step 3: The expressions are equivalent because they both equal the same value.

Of the options provided, the correct missing step is:

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