Please show me how to work it out

Question

The length of a rectangle is three inches more than the width. The area of the rectangle is 378 inches. Find the width of the rectangle.

Answer 1

i have been trying to work on this but I'm stuck.  This is what I have so far:

L=W + 3

378= (W+3) W

378= W² + 3W

 

from there I'm stuck! Sorry

Answer 2

w(w + 3) = 378

w² + 3w = 378

w² + 3w - 378 = 0

(w + 21)(w - 18) = 0

 

w + 21 = 0

w = -21

Measurements are positive, so this is out.

 

w - 18 = 0

w = 18"