A bank teller has 47 $20 and $5 bills in her cash drawer. The value of the bills is $490. How many $20 bills are there?

A bank teller has 47 $20 and $5 bills.

The value of the bills is $490.

Number of $20 bills --> x

Number of $5 bills --> y

x + y = 47 --> x = 47-y

20x + 5y = 490 --> 20x = 490-5y

so

20(47-y) = 490 -5y

940-20y = 490-5y

940-490 = -5y+20y

15y = 450

y= 30

so

x = 47-30

x = 17

IN TOTAL --> 17 $20 bills and 30 $5 bills.

i think the length is 12 and the width is 17