We will solve as follows:
*We will have that the following function models the perimeter of the rectangle:
[tex]2l+2w=78[/tex]Here l is the length and w is the width. Now, we replace l and solve for w:
[tex]\Rightarrow2(25)+2w=78\Rightarrow2w=28\Rightarrow w=14[/tex]So, the width is 14 ft.