Find the missing side. Approximate the answer to three decimal places when appropriate.

A = 15 yd C = 25 yd

I have no clue on how to do this one. Please any help would be appreciated.

A^2 + B^2 = C^2

A^2 + B^2 = (25)^2,
(15)^2 + B^2 = 625,
225 + B^2 = 625,
B^2 = 400,
B = 20.