Question

Abbi has $400 in $5 bills. If she has 38 bills, how many of them are $20?

Assign two variables and two equations. Please solve.

Answer 1

$400 in $5 = 80 bills
it says she has 38 bills so she has 20. 400/20= 20

Answer 2

f=5 dollar bills
t=twent dollar bills

38 total bills
f+t=38

400 in bills
400=5f+20t

we have
f+t=38
5f+20t=400
multipy first equation by -5 and add to second equation

-5f-5t=-190
5f+20t=400 +
0f+15t=210

15t=210

divide both sides by 15
t=14

subsitute
t+f=38
15+f=38
f=23


23 five dolar bills
15 twenty dollar bills