If you start at 740 cards total and you subtract the 20 more cards Gil had and the 120 cards more that Meg had you will be left with 600 cards and then you divide that by the 3 of them and each of them would get 200 cards.
To double check your work you would add them all up the 200 cards Alex has plus the 220 that Gil has and the 320 that Meg has and you get a total of 740 cards.
