Hello!
The answers are:

Why?
Since we are working with a right triangle, we can use the Pythagorean Theorem, which states that:

Then, we are given the following information:
Let be "a" the shorter leg and "b" the the longer leg of the right triangle, so:

We can see that we need to perform the notable product, so:

We have that the obtained equation will be equal to 0 if: b is equal to 0 or b is equal to 28:


So, since we are looking for the side of a leg, the result that we need its 28 feet.
Hence, we have that the answers are:

Have a nice day!