Answer:
85 ft
Explanation:
The Pythagorean theorem tells you the length of the hypotenuse (c) is related to the lengths of the legs (a, b) of a right triangle by ...
c^2 = a^2 +b^2
c^2 = (40 ft)^2 +(75 ft)^2 = 7225 ft^2
c = √(7225 ft^2) = 85 ft
The length of the missing side is 85 ft.