The area of this rectangle is 80ft^2. what is the length and width.

width: x+16
length: x

what is x for width?
what is x for length?

Area=LW
80=area
L=x+16
W=x
80=(x+16)(x)
80=x^2+16x
minus 80
0=x^2+16x-80
factor
0=(x-4)(x+20)
set to zero
x-4=0
x=4

x+20=0
x=-20, false since you can't have negative degrees (except in trig)

x=4

legnth=4+16=20 ft

width=4ft

x=4
legnth=20ft
width=4ft