19. Tom has a collection of 30 CDs and Nita has a collection of 18 CDs. Tom is adding 1 CD a month to his collection while Nita is adding 5 CDs a month to her collection. Find the number of months after which they will have the same number of CDs. Show your work.

m = number of months...
30 + m = 18 + 5m
30 - 18 = 5m - m
12 = 4m
12/4 = m
3 = m <== they will have the same amount at 3 months

check...
30 + 3 = 18 + 5(3)
33 = 18 + 15
33 = 33 (correct)