Answer:
a = 80
Explanation:
This is a right triangle so 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 + 60^2 = 100 ^2
a^2 +3600=10000
Subtract 3600 from each side
a^2 = 10000-3600
a^2 =6400
Take the square root of each side
a = sqrt(6400)
a = 80