Barry's deck has 50 blue and 60 red so his ratio of blue cards to red cards is 50/60 which can be written as 5/6, or 5:6.
So max also has 50 blue cards, but his ratio of blue cards to red cards is 5:9. This means that for every 5 blue cards he has, he also has 9 red cards. He has 50 blue cards, so he also has 90 red cards.
