Answer: There are 8 $5 bills, 2 $10 bills, and 6 $1 bills.
Step-by-step explanation: If you have 6 more $5 bills than the number of $10 bills, that means you have at least 6 to start off with. This also means you have at least 1 $10 bill. If you have 1 $10 bill, then you have 3 $1 bills as well. Adding those bills up, you get $43. From here, you know you need $3 more. Meaning you have to add another $10 bill. Since you added another $10 bill, you have to equal out the $5 bills.
So if you know you have 2 $10 bills and 6 $1 bills, you can determine that you need 8 $5 bills to complete the set.
2 $10 = $20
8 $5 = $40
6 $1 = $6
$20 + $40 + $6 = $66