how did u get what r in red?
I assumed couple of things in the question, which I am not sure if right way to do, but otherwise question was also not very clear in details.
As we know the total sale amount is 67 and it comprises $13 and $5 sale.
So I assumed it would comprise atleast one $13 sale so 67-13 = 54 but this is not a multiple of 5 so there may be more than one sale of $13. Tried 54-13 = 41 but this is again not a multiple of 5 so keep on doing this until I get the number which is multiple of 5, which became the number of sales of $5.
Hope this clarifies.