Answer:
In 3 months
Step-by-step explanation:
Henrik buys at 40 cards/month.
Kharif sells at 20 cards/month, from a starting collection of 180 cards.
At x months, Kharif will have 180-(20 cards/month)(x months)
At x months, Kenrik will have 0 + (40 cards/month)*x {We must assume he starts with 0 cards, since no information is given.]
We want to know the nmonths until Both have the same number, so set their equations equal to each other:
180-(20 cards/month)(x months) = 0 + (40 cards/month)*x
180 = x(40 cards/month + 20 cards/month)
180 = x(60 cards/month)
x = 3 months
In 3 months, both will have 120 cards
