A bank teller has a total of 124 bills in fives and tens. The total value of the money is $840. How many of each kind does he have?

Answer 1

first, we represent the unknowns using variables:
let x = number of 5-dollar bill
since according to first statement, he has a total of 124 bills in 5 and 10,
let 124 - x = number of 10-dollar bill
now we set up the equation,, according to the second statement, the total value is $840. thus,
5x + 10(124-x) = 840
solving for x:
5x + 1240 - 10x = 840
-5x + 1240 = 840
-5x = -400
to get x alone, we divide both sides by the numerical coefficient of x which is -5:
(-5x)/(-5) = -400/(-5)
x = 80 five-dollar bill
124-x = 44 ten-dollar bill

hope this helps~ :0