PLEASE ANSWER ASAP!!! I WILL MAKE YOU BRAINLIST Find the length of the third side. If necessary, round to the nearest tenth.

Answer:
15
Step-by-step explanation:
a^2 + b^2 = c^2
20^2 +b^2 = 25^2
400 + b^2 = 625
-400 -400
b^2 = 225
b = √225
b = 15