What are the rectangles dimensions?

Question

The width of a rectangle is 40 cm less than its perimeter. The rectangle's area is 102 sq cm

Answer 1

Okay 2w+2l=p, and w=p-40, or 40+w=p.
So, 2w+2l=40+w, or w=40-2l.
And wl=102.
So, (40-2l)l=102.
Or, 2l^2-40l+102=0.
Divide each side by 2, giving you l^2-20l+51=0.
Factoring it, and you get (l-17)(l-3)=0.

So, you can have length=17, and width=6.
And you can have length=3, and width=34.

Answer 2

I've already answered one of your homework problems, get out your book and figure it out yourself.