Final answer:
The property that justifies the equation 12 + (4 + 10) = 12 + (10 + 4) is called the commutative property of addition.
Step-by-step explanation:
The property that justifies the equation 12 + (4 + 10) = 12 + (10 + 4) is called the commutative property of addition.
This property states that when adding two or more numbers, the order in which the numbers are added does not affect the sum. In other words, you can rearrange the order of the numbers being added and the result will be the same.
For example, in the given equation, we can add the numbers inside the parentheses first: 12 + (4 + 10) = 12 + 14 = 26. Then, we can add the numbers outside the parentheses: 12 + (10 + 4) = 12 + 14 = 26.