Respuesta :
Answer:
Step-by-step explanation:
x = $5 dollar bills
 y = $10 dollar bills
 x + y = 15
 5x + 10y = 120
5x + 10(15-x) = 120
 5x + 150 - 10x = 120
 -5x = -30
 x = 6, so y = 9
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There are six $5 bills and nine $10 bills.
Multiples of 5s will only end with 5 or 0. Â 5 times any odd number will always end with 5 and 5 times any even number will always end with 0