Christopher is going to install wallpaper on the four walls of his room. two of the walls are 14 feet long by 9 feet high. the other two walls are 20 feet long by 9 feet high. his options at the wallpaper store are below.
one single roll of wallpaper costs $20 and covers 18 square feet of area.
one double roll of wallpaper costs $40 and covers 54 square feet of area.
what is the minimum cost of installing the wallpaper on the four walls of christopher's room?
$

2 of the walls are 14 ft by 9 ft
A = L * W
A = 14 * 9 = 126 sq ftand since there is 2 of them...2(126) = 252 sq ft

2 of the walls are 20 ft by 9 ft
A = L * W
A = 20 * 9
A = 180 sq ftand since there are 2 of them ..2(180) = 360 sq ft

so for all 4 walls, we have : 252 + 360 = 612 sq ft

54 * 11 = 594 sq ft...so we need 11 double rolls...which costs 11(40) = $ 440
18 * 1 = 18 sq ft and we need 1 single roll...which costs $ 20

so we have 612 sq ft to cover11 double rolls cover 594 sq ft and cost 440...and 1 single roll which covers 18 sq ft and cost 20
for a total cost of : $ 460 <==

Horizontal change or the change of x