I’m pretty sure the answer is 4 because to find the area of a triangle the formula is 1/2 x base x height. So with these numbers it would be 1/2 x 4 x 5=10. Then I think you find the area of the rectangle which is base x height so 3x2=6. Then I think you do 10-6=4.
Hope this helps (don’t worry that wasn’t easy!)