A right triangle has a hypotenuse of length 25 and a leg 15 what is the length of the other leg?

Pythagorean theorem:

A2 + B2 = C2

If, A = 15 and C = 25, solve for B.

152 + B2 = 252

225 + B2 = 625

B2 = 625 - 225

B2 = 400

B = sqrt(400)

B = 20

Therefore, the missing side is 20.