The cost to mail a 2-lb package is $7.
The cost to mail a 2-lb, 1 oz package is $7+$0.30(1).
That to mail a 2-lb, 2 oz package is $7+$0.30(2) = $7.60.
Following this pattern, the general formula is f(x) = $7 + $0.30x, where x represents the number of ounces OVER 2 lb.
Y=18 is the correct answer
