Answer:
The third side is sqrt(77)
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
2^2 + b^2 = 9^2
4+ b^2 = 81
Subtract 4 from each side
b^2 = 81-4
b^2=77
Take the square root of each side
sqrt(b^2) = sqrt(77)
b = sqrt(77)
The third side is sqrt(77)