Answer is
.
Let the length of the other leg be x. According to the Pythagorean theorem the sum of the squares of the lengths of the two legs of a right triangle equals the square of the length of the hypotenuse.
Therefore we have the equation:
√8^2 + x^2 =5^2
Simplifying this equation we get:
8 + x^2 = 25
Subtracting 8 from both sides we get:
x^2 = 17
Taking the square root of both sides we find:
x = √17
So the length of the other leg of the right triangle is √17.