I don't really get your question.
I would tell you to see that you have a rectangle of area that is cut in two pieces.
Use a geometry formula to calculate the are of the region...
I know that the area of a triangle is A=(1/2)(b)(h)
The triangle equation that is given is y=(h/b)(x)
My question is how to calculate the area of the region with A=(1/2)(b)(h)