Here we must check what each person is calculating. First, we consider Susan's method. She has suggested that we multiply the cost per soda, that is dollars/soda by the number of sodas required, we get the total cost. Assuming that 18 sodas are required and each costs $0.20, the total cost according to Susan is $3.60.John suggests we divide the cost of a 12 pack of soda by the number of sodas required. Considering a 12 pack of soda costs $12 and the same amount of sodas, 18, are required, we get that each soda costs $0.66.Looking at these answers, we see that Susan has suggested a correct method to calculate the amount of money needed to buy a number of sodas. John has suggested the amount each person would have to contribute if everyone at the party was trying to buy a 12-pack of soda; regardless of whether more or less than a 12-pack is required. Susan is correct because to get the total cost, we multiply the unit price by the number of people attending.