The formula for the area of a triangle is A = (base · height)/2, but when we look at this problem, there's no base or height!
Looking at the triangle on the right, we can use the Pythagorean Theorem to find the height:
h² + 16² = 20²
h² + 256 = 400
h² = 144
h = ± 12
In this case, the height is 12 because you can't have negatives when you are working with lengths of sides and other things like this in geometry.
So now we've found the height, but we still don't know the full base! So, we can use the height that we just found to use the Pythagorean Theorem for the left triangle!
B² + 12² = 15²
B² + 144 = 225
B² = 81
B = ±9
So once again, our answer is just 9.
But, because the base is CB, we have to add:
b = 9 + 16
b = 25.
Now we have the base and height, so we can put them into our formula to solve for the area of the triangle:
A = (25 · 12) / 2
A = 300 / 2
A = 150