Question 287301
A diagonal of a rectangle forms a right triangle with its sides.
L=d-13
w=d-6
L^2+w^2=d^2
approximate answers
d=31.49,   L=18.49,   w=25.49

Your solution.
55^2+48^2=73^2
The sides are 55 and 48 and the diagonal is 73.
Those dimensions do indeed form a right triangle but they meet none of the criteria for the given rectangle and diagonal.
The length 55 is not 13 feet shorter than the diagonal 73.
The width 48 is not 6 feet shorter than the diagonal 73.