You're just simply going to use the equation for surface area which is

(

) so you're going to plug in and then solve to get the inches squared of all the sides that Erin would cover with the contact paper.
Once you get that number you're going to multiply it by .08 to get the price.
Answer:
400
Step-by-step explanation:
12000 X 60%=7200-parents
12000-7200=4800-owen
4800/12=400 is what owen will save monthly
Let C = cost to rent each chair
Let T = cost to rent each table
4C + 8T = 73
2C + 3T = 28
Multiply the 2nd equation by (-2) and then add the equations together
4C + 8T = 73
-4C - 6T = -56
2T = 17
T = 17/2 = 8.5
Plug this in to the 1st equation to solve for C
4C + 8(17/2) = 73
4C + 68 = 73
4C = 5
C = 5/4 = 1.25
So the cost to rent each chair is $1.25 and the cost to rent each table is $8.50