Answer:
is used to find 'x'.
Explanation:
Let the length of other leg be 'x'.
Since we have given that one of the legs needs to be 7 feet longer than the other leg.
So, Length of one leg = x+7
Hypotenuse of the right triangle = 13 feet.
Since it form right angle triangle.
so, we can use "Pythagorus theroem".

Hence,
is used to find 'x'.