Maggie's class bought three books at the book fair the book cost $15, $9 and $12. use parenthesis to write two different expressions and find how much the class spent in all. which property does the pair of expressions demonstrate

To determine the total class the whole class spent, you just have to simply add the individual costs of the three books. Using parenthesis, the solution can be written in the following two ways:

($15 + $9) + $12 = $36
$15 + ($9 + $12) = $36

No matter where you put the parenthesis, the final answer doesn't change. This is because of the Commutative Property of Addition. The order does not matter.