Answer:
Mason wins after 18 total moves
Step-by-step explanation:
Mason's optimal strategy is to keep the total number of marbles at 11n+1, so he will take 10 marbles to start. For each move Jason makes, Mason will take a number of marbles that makes the sum from the two turns be 11.
After each of Mason's 9 turns, the number of remaining marbles will be ...
89, 78, 67, 56, 45, 34, 23, 12, 1
It doesn't matter how many marbles Jason takes. He will lose on his 9th turn.