#### Answer

30 $ft^{2}$

#### Work Step by Step

Find the height by using the Pythagorean Theorem:
$a^{2}$+$b^{2}$=$c^{2}$
$3^{2}$+$b^{2}$=$5^{2}$
9+$b^{2}$=25
$b^{2}$=16
b=4 (This is your height of the trapezoid.)
We use the formula for the area of a trapezoid to obtain:
A=$\frac{1}{2}$h($b_{1}$+$b_{2}$)
A=$\frac{1}{2}$(4)(6+9)
A=$\frac{1}{2}$(4)(15)
A=30