Answer:
The third piece of wood that for denesh need to create to form a right triangle is:
25 feet.
Explanation:
We are given two shorter legs of a wood of lengths as:
7 feet and 24 feet.
We know that in a right angled triangle with two shorter sides as a and b the longer length or the hypotenuse of the triangle of length c is given by Pythagorean Theorem as:

We have:
a=7 and b=24
Hence,

Hence, the length of the third piece of wood should be:
25 feet.