Question

A certain mail service charges $15 for an overnight package, plus 18 cents per pound. Find the cost of mailing a 40-pound package through this company.

Answer 1

Cost = $15 + $ .18x

y = .18 (40) + 15
y = 7.2 + 15
y = 22.2

so the answer is $22.20 

check:

22.20 = .18x + 15
7.2 = .18x 
x = 40