Given:
Total income form tips = $131
His tips consisted of $1 bills and $5 bills only.
Total number of bills = 47
To find:
The number of $5 bills.
Solution:
Let x be the number of $1 bills and y be the number of $5 bills.
Total bills :
...(i)
Total income :
...(ii)
Subtract (ii) from (i), we get




Therefore, the number of $5 bills is 21.