#### Answer

$x^{2} +2x-15$

#### Work Step by Step

Recall, the area of a rectangle equals length times width, or, in this case, (x+5)(x-3). In order to multiply binomials, we use the distributive property. However, recall that in order to use the distributive property with binomials, we must multiply both things in the first set of parenthesis by both things in the second set of parenthesis. Thus, we distribute the x to the (x-3) and then distribute the 5 to the (x-3). We then combine like terms to obtain the answer:
$x^{2} +2x-15$