Answer:
a = 8.7
Explanation:
The Pythagorean theorem is
a^2+b^2 = c^2 where a and b are the legs and c is the hypotenuse
a^2+5^2 = 10^2
a^2 +25 = 100
a^2 = 100-25
a^2 = 75
Taking the square root of each side
sqrt(a^2) =sqrt(75)
a =8.660254038
Rounding to the nearest tenth
a = 8.7