I didn't use the midpoint formula.

If the base is 8, then the area of the unshaded triangle is 6 via (.5)(4)(3). Based on what they gave us in the question.

Then if the midpoint of line AC is 5, then AC is equal to 10. So for the whole triangle I used the p. theorm. Which was a^2+8^2=10^2. So I got a or height is equal to 6.

Then I used the area formula (.5)(6)(8) to get 24.

So the whole area is 24, and the area of the unshaded region is 6 so 24-6 I got the area to be 18.

Let me know.

Thanks.