#### Answer

9

#### Work Step by Step

We follow the instructions to plug 2 in for a and 5 in for b, and then we use the order of operations to simplify. According to the order of operations, we simplify inside parentheses, then we simplify powers, then we multiply and divide, and finally, we add and subtract. When we do this, we find:
$(2-5)^{2} = (-3)^{2}=9$