If g = 77 cm and h = 85 cm, what is the length of f? my formula is a right-triangle.

If we are looking for the hypotenuse the answer is, 114.69. If the h is the hypotenuse then you would have 36 for leg b. 

For this problem use the Pythagorean therom. a^2 + b^2 = c^2

So plug in your values.
if h is the hypotenuse then its 77^2 + f^2 = 85^2
5929 + f^2 = 7225
f^2 = 1296
f=36