Jenna has more.
If Max gives 16 cards to Jenna, then he has 16 cards less. 20-16=4... Max has only 4 cards left.
Similarly, because Jenna gains 16 cards, 50+16=66. Thus Jenna has 66 cards.
If Max has 4 cards, and Jenna has 66, Jenna clearly has way more.
Hope that helps :))