You have $80 to spend on refreshments for a party. Large bags of chips cost $2.50 and sodas cost $0.50. You need to buy exactly five times as many sodas as bags of chips. How many bags of chips and how many sodas can you buy?
Let C = number of bags of chips and S = number of sodas.
2.5*C + 0.5*S = 80 ...(1)
S = 5*C ...(2)
Replace S in (1) using (2)
2.5C + 0.5*5C = 80
2.5C + 2.5C = 80
5C = 80
C = 80/5 so C = 16
Put this back into (2)
S = 5*16 so S = 80
