12 people buy their purchases for a 10-day camp. they agree to share the materials equally. if three more people join the group and they didn't buy more materials how many days would the purchases last if each person still had the same amount of stuff.

Okay so there is enough material for 12 people for 10 days but there is 15 of them we have to see how long they can last with that material i am going to need more info to complete this but let me do you an example for some help lets say a whole 10 day package is 10 crackers so if there is 12 packages then that means there is 120 crackers  if there were 12 people every one would get 10 but there is 15 so we need to divide 120 and 15 which comes out to 8 so that means every body gets eight crackers whick also means they only last eight days but sense the question is not complete i can not help you much i nee the amount that is in the packages that they purchased