Answer:
8 ft, 15 ft, 17 ft
Explanation:
Let x feet be the length of the side along the building. If the hypotenuse is 9 feet longer than the side along the building, then the length of the hypotenuse is x+9 feet. If the third side is 7 feet longer than the side along the building, then the length of the third side is x+7 feet.
This triangle is right triangle. By the Pythagorean theorem,

The length of the side cannot be negative, thus x=8 ft. Then x+7=15 ft, x+9=17 ft.