How to write the perimeter of a rectangle in terms of its length and width

Question

I was given a word problem, of which I stink at, where I first have the perimeter of the rectangle in 200in, and I have to express length as a function of width. I have no idea how to do this. I know that P=2(l+w)...

In the second part I have the same rectangle but now I have to write the Area of the rectangle in terms of width. Would this be A=p/e *w? 

Answer 1

P = 2( length + width )

200 = 2 ( length + width )

100 = length + width

100 - length = width