algebra
posted by Anonymous .
A bank teller has 35 bills in $5, $10, and $20 denominations. The total value from these bills is $370.The total number of $10 bills and $20 bills is 7more than the number of $5. How many bills of each denomination?

No. of $5=bills a, $10 bill=b and $20 bill=c
Then a+b+c=35
5a+10b+20c=370, and
b+c=a+7.
Substituting value of b+c in first eq.,
a+(a+7)=35 or 2a=28 or a=14 and
b+c=3514=21.
Substituting value of a in second eq., 14x5+10b+20c=370 or 10b+20c=37070
Or 10b+20c=300 or b+2c=30
Subtract from this the eq. b+c=21 and we get c=3021=9. thus b=35149=12.
Check:14x5+12x10+9x20=370
70+120+180=370 OK.