At a park, a landscaper wishes to plant a uniform border of tulips around the outside of a 18m by 12m rectangular garden. The garden will look best if the area of the tulip border is half the area of the garden. How wide should the border be?

2 answers

P=2(18)+ 2(12)= 36 +24+ 60
A+18x12=216
Tulip border= 216/2=108

(18+x)(12+x)=(18x12)/2 +216
216+18x+12x+x^2=108+216
x^2+30x-108=0
cannot factor
quadratic equation = -40.82 or -20.82
Guidance as to where I am going wrong?