For this case we have that if Molly spent all the spool ribbon with 12 people, then "r" would be given by the product of 12 for the amount of ribbon that each person received, that is:
Thus, the spool initially had 36 feet of ribbon.
If Molly also keeps 3 feet of ribbon, then the value of "r" is given by:
In this case, the ribbon spool initially had 39 feet of ribbon.
Answer:
shared between 12 people
shared between 12 people and Molly