Answer:
I think n is meant to be 15
12 balloons total
u blow up 1/3.....1/3(12) = 12/3 = 4....so u blow up 4 out of 12...thats 4/12
ur friend blows up 5...he blows up 5 out of 12....thats 5/12
so 4/12 + 5/12 = 9/12....9/12 are blown up.....that leaves 3/12 or 1/4 left to blow up
You could multiply 1/4 by 3 and 1/6 by 2. You would get 3/12 and 2/12. The common denomonator is 12. 4 and 6 are both multiples of 12.