Find the area of the shaded portion below.

the shaded area is essentially the area of the trapezoid minus the area of that semi-circle.

the area of the trapezoid is 

\(\frac{50+80}{2} \cdot (20 \cdot 2)\)

= \(\frac{130}{2} \cdot 40\)

= \(65 \cdot 40\)

= \(2600\)

the area of the semi-circle is 

\(\frac{20^2 \cdot \pi}{2}\)

= \(\frac{400 \cdot \pi}{2}\)

= \(200 \pi\)

so, the area of the shaded region is \(2600 - 200\pi\).

hope this helped! please let me know if you have any questions