I believe the answer is 5 months; however, I did it the long way. Explain how to find the answer.
Tom has a collection of 30 CDs and Nita has a collection of 15 CDs. Tom is adding 1 CD a month to his collection while Nita is adding 4 CDs a month to her collection. Find the number of months after which they will have the same number of CDs.
T=30+1*time
N=15+4*time
if T=N, then
30+time=15+4time
solve for time