You can
put this solution on YOUR website!Let's take X as the width and 2x-5 as the length.
That means:

(we multiplied by 2 because perimeter contains 2 of the length and 2 of the width)
That becomes:
Which simplifies to:

,

,

;
That means that the width is 40 and the length is 75 (40*2-5)
Done. =)