Answer:
5
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 + 10^2 = (5 sqrt(5))^2
a^2 +100 = 25(5)
a^2 +100 = 125
a^2 = 125-100
a^2 = 25
Taking the square root of each side
sqrt(a^2) = sqrt(25)
a = 5