Can someone help me please

17 inches

Explanation:
The Pythagorean theorem states that a^2+b^2=c^2 when c is the longest side (the hypotenuse) and a and b are the other two sides. This theorem can only be applied to right triangles.

First, plug the values into the formula.
a^2+b^2=c^2
8^2+15^2=c^2
64+225=c^2
289=c^2
Take the square root of both sides
c=17

I hope this helps!

The answer is d 18ft