Question

To prove the equivalence \( 12a + 10 + a = 10 + a + 12a \) using the Commutative Property, we need to rearrange the terms in the expression.

The correct missing step would be:

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

Now let's rearrange the terms:

**Step 2:** \( 10 + 12a + a = 10 + a + 12a \) (using the Commutative Property).

This means that the correct missing step to complete the proof would be:

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

However, looking at the provided options, the one that directly correlates with this logic is:

**10 + 12a + a = 10 + 13a**

So, writing that format eventually summarizes that:

**10 + 12a + a = 10 + 13a.**

Thus, the answer is:
**10 + 12a + a = 10 + 13a.**

If your choices need to match exactly to one from your list, it seems the best fit would be:

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

This represents a symmetry, leading towards the same side of the equation equivalently showing the process of reaching an equivalent fact through switching the placement of the components in the equation.