Math please help!!please help!?

This is a tricky question and requires some common sense and logic. First of all, if 7 of each was given away, then there are 7 items left; 28-3(7) = 7. Also, since you gave 7 of each, then 7($3) + 7($4) + 7($5) = $84 was given away and now $108-$84 = $24 is left over. Now it gets a bit tricky. You have to do some trial and error because you don't know which of the 2 you have left. However, no matter how many caps you choose between 1 and 7, you can never get $24 and add up to 7 with one more item. So, you must have ran out of caps. Therefore, you have two equations: # Balloons + # Candy = 7 and $3*balloons + $4*candy = $24, and the only combination that works is 4 additional balloons and 3 candy, so the final answer is : 7 caps, 11 balloons, and 10 bags of candy.