The property shown in #11 is the Associative Property of Addition.
In short, the associative property of addition states that no matter how an additive expression is grouped, the quantity will turn out the same. In this case, the answer is going to be equal whether you decide to add 5 and 8 first or 8 and 11 first.
Pretty sure it would be D
Good luck on your finals!
First: 7cm, 7cm, 11cm
second: 19cm, 3cm, 3cm
