Wythoffs Game -Game Theory

Question

Suppose in the Wythoff’s game there are 40 matches in the first pile and 20 in the second pile and it is your turn to play. How would you play?

Please assist in how to complete this problem.

Answer 1

$(20,12)$ is a safe pair so reduce the $40$ pile to $12$ and you win.

For a table of safe pairs see page 8 of this, e.g.