Suppose that Jackie had played $n$ games before her last game. Since she scored an average of 20 points per game over these $n$ games, then she scored $20n$ points over these $n$ games. In her last game, she scored 36 points and so she has now scored $20n+36$ points in total. But, after her last game, she has now played $n+1$ games and has an average of 21 points scored per game. Therefore, we can also say that her total number of points scored is $21(n+1)$. Thus, $21(n+1)=20n+36$ or $21n+21=20n+36$ and so $n=15$. This tells us that after 16 games, Jackie has scored $20(15)+36=336$ points. For her average to be 22 points per game after 17 games, she must have scored a total of $17 \cdot 22=374$ points. This would mean that she must score $374-336=38$ points in her next game.