If all the 12 people and her get 3 feet then we can simply multiply 3 by the number of people which is 13 and we get 39 after doing the multiplication.
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.
