Part A
Let at-store service be x
Let on-site service be 3x
Let by-mail service be x - 10
Part B
15 services on-site
40 services at-store
5 services by-mail
Total sales = $2650
∴ 15(3x) + 40(x) + 5(x-10) = 2650
Simplify
15(3x) + 40(x) + 5(x-10) = 2650
45x + 40x + 5x - 50 =2650
90x = 2700
90x/90 = 2700/90
x = 30
Part C
Since x = 30 and services on-site = 3x we can now solve for on-site
on-site = 3x = 3(30) = 90
On-site 1 repair cost $90
