check the picture below.
so, when we have a line from a 90° angle running perpendicular to the opposite side, like in this case, we end up with three similar triangles, a large one containing the other two, a medium and a small one.
now, using the sides proportions as you see there, of the small and large one, we get that much.
Answer: 200
Step-by-step explanation:
since 10 is one part
10 x 20 = 200