Since it is a right triangle, you can use the Pythagorean Theorem to find the length of the missing side. a^2 + b^2 = c^2 (a and b are the legs, c is the hypotenuse) In this triangle, a=21 and c=25. Find b. 21^2 + b^2 = 25^2 441 + b^2 = 625 b^2 = 184 b = 13.6
