This is a multistep problem. So, let's split it up.
Finding the height:
We need to look at the equation for find the diagonal of a triangle.
a²+b²=c²
We don't have leg one, but we have leg two. If we subtract the longer base by the shorter base, we have leg two.
11-7=4
a²+4²=5²
a²+16=25; let's subtract 16 from both sides.
a²=9
a=3
So, the height is 3.
Finding the area of the trapzoid:
Let's look at the formula for finding the area.
(b1+b2)(h÷2)=A; let's fill the variables in.
(7+11)(3÷2)=A
(18)(1.5)=A
27=A
So, the area of the trapezoid is 27 in²