How are they equal? If you take a line from G and drew it down, you'd get a right triangle. Essentially you're adding a rectangle plus a triangle. Wouldn't the trapezoid be larger as a result?
The trapezoid would be larger than the rectangle contained within it, yes. However, we're not trying to figure out the size of the trapezoid relative to a 5 by 4 rectangle contained within it. Instead, we're comparing the size of the trapezoid to a separate 8 by 3 rectangle. And on that basis, the trapezoid in the question and the separate 8 by 3 rectangle have equal area.
2 Explanations