The rectangular poster shown measures 2w-30 by w. the poster has an area of 5400 cm2. what is the value of w?

1. To solve this problem, you must use the formula of the area of a rectangle, which is shown below:

 A=lxw

 "A" is the area of the rectangle (A=5400 cm²).
 "l" is the lenght of the rectangle (l=2w-30).
 "w" is the width of the rectangle.

 2. When you substitute l=2w-30 into the formula A=lxw, you have:

 A=lxw
 5400=(2w-30)(w)
 5400=2w²-30w
 2w²-30w-5400=0

 3. Now you have a quadratic equation. When you solve it, you obtain the value of "w". Then:

 w=60 cm