SOLUTION: a bank teller has 54 $5 and $20 bills in her cash drawer. The value of the bills is $780. How many $5 bills are there. Could you please show the work. Thanks!

Question 519004: a bank teller has 54 $5 and $20 bills in her cash drawer. The value of the bills is $780. How many $5 bills are there. Could you please show the work. Thanks!
Found 2 solutions by Maths68, jessica43:
Answer by Maths68(1474) (Show Source): You can put this solution on YOUR website!
Let
$5 bills = x
$20 bills = 54-x

$5*(x)+$20*(54-x)=Total Amount
5x+20(54-x)=780
5x+1080-20x=780
-15x=780-1080
-15x=-300
-15x/-15=-300/-15
x=20
$5 bills = x = 20
$20 bills = 54-x=54-20=34
Check
5*20+20*34=780
100+680=780
780=780

Answer by jessica43(140) (Show Source): You can put this solution on YOUR website!
To solve these types of problems, you need to write two equations using what you know.
First, you know that you have two types of bills and a total of 54 bills:
F + T = 54 (F=number of $5 bills, T=number of $20 bills)
Second, you know that the total value of these bills is $780:
5F + 20T = 780
Next you want to get rid of one of the variables (F or T) by plugging one of the equations into the other. The first equation can be rewritten by subtracting F from both sides:
F + T = 54
T = 54 - F
Now plug this equation into the second equation for T, and solve for F:
5F + 20T = 780
5F + 20(54-F) = 780
5F + 1080 - 20F = 780
1080 - 15F = 780
-15F = -300
F = 20
So the bank teller has 20 $5 bills.
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