Answer:
a = 15
Step-by-step explanation:
Since this is a right triangle, we can use the Pythagorean theorem
a^2 + b^2 = c^2 where a and b are the legs and c is the hypotenuse
a^2 + 20^2 = 25^2
a^2 + 400 = 625
Subtract 400 from each side
a^2 = 225
Take the square root of each side
sqrt (a^2) = sqrt(225)
a = 15
