Since these are right triangles, we can use Pythagorean Theorem.
Pythagorean Theorem: a^2 + b^2 = c^2
50^2 + 20^2 = c^2
2500 + 400 = c^2
2900 = c^2
c = sqrt[ 100 * 29]
c = 10 sqrt[29]
In the boxes, a = 10, b = 29.
Hope this helps!! :)
