You find the area of a triangle by using 1/2*b*h where b is the base and h is the height. since we already know the area is 20 and the height is for you plus them in so the problem would be 20= 1/2 (b) (4) then you multiply what you know together to get 20= 2b and then isolate the b by dividing both sides by two so the base should be 10 m
