In how many ways type of question

In how many ways we could give 81 cents change if we only have 2 and 5 cent coins.
Answer is 8

Max sum of 5 cents = 75 because if it goes to 80 then a 2 cent will make it 82
Sum of 5 cents + sum of 2 cents = 81 cents
Following are the combinations:
75+6
65+16
55+26
45+36
35+46
25+56
15+66
5+76