Answer: After 8 months they will have equal number of DVD's.
Step-by-step explanation:
Given: Kaleb has 45 DVD's in his collection and Eileen has 61.
Let x= Number of months
If Kaleb buys 4 new DVD's each month and Eileen buys 2 new DVD's each month , then
Total DVD's Kaleb has = 45+4x
Total DVD's Eileen has = 61+2x
When they has equal DVD's , then
[tex]45+4x =61+2x\\\\\Rightarrow\ 4x-2x=61-45\\\\\Rightarrow\ 2x=16\\\\\Rightarrow\ x=\dfrac{16}{2}\\\\\Rightarrow\ x=8[/tex]
Hence, after 8 months they will have equal number of DVD's.