What is the area of trapezoid with vertices of (-4,5), (1,5), (-8,-3), (5,-3)?
make a sketch
from (-4,5) and from (1,5) , drop perpendiculars to the longer base line.
You now have a rectangle + 2 triangles.
By simply "counting" you can determine the base and height of each rectangle and the sides of the rectangle.
Easy from there.