Gregory teaches martial arts. He charges a one time processing fee of 5 dollars and the cost of each classes is shown below. Let x represent the number of classes and y represent the cost of classes. Based on this information, what will it cost to take 10 classes?
cpst of classes not inculding processing fee.
number of classes, x. 1 : $15.00 2: $27.00 3: $39.00 4: $51.00. cost of classes, y. my teacher came up with c= 5.00+10(5.00) and the answer is $128.00. but i dont understand how she got that.

Question

Gregory teaches martial arts. He charges a one time processing fee of 5 dollars and the cost of each classes is shown below. Let x represent the number of classes and y represent the cost of classes. Based on this information, what will it cost to take 10 classes?
cpst of classes not inculding processing fee.
number of classes, x.    1 : $15.00   2: $27.00 3: $39.00  4: $51.00. cost of classes, y. my teacher came up with c= 5.00+10(5.00) and the answer is $128.00. but i dont understand how she got that.

anonymous · Answer

Insufficient information. We need to know which classes are taken. for instance the cheapest would be class 1, costing 5 +10(15) = $155, and the most expensive is class 4, 5 + 10(51) = $515. 
your teachers answer of $128 is not in this range, and is therefore impossible. It is unlikely your teacher is so wrong. you have probably misunderstood either the question or your teachers answer.