The French club sold rose bouquets and chocolate hearts for Valentine's Day. The roses sold for $5 and the hearts sold for $3. The number of bouquets sold was 15 more than the number of hearts sold. If the club collected a total of $339, how many of each gift was sold?
To solve this you have to express the quantities of both as a function of one. For example since the number of bouquets sold was 15 more than the number of hearts, you can express the bouquets as X and then the number of hearts as X-15 rather just Y.
Then you have the following equation.
Factor it out to get
Check it's right by plugging these numbers into the formuler 5x+3y=339
So they sold 48 roses and 33 hearts.