let x = number of $10 billsA cashier has $645 in 10 dollar and 5 dollar bills. There are 90 bills in all. How many of each does the cashier have?

y = number of $5 bills

A cashier has $645 in 10 dollar and 5 dollar bills.

10x + 5y = 645

There are 90 bills in all.x + y = 90

solve the system of equations using your favorite method.