17. 1/3 × 1/2 × 1/2 = 1/12
18. 1/3 × 1 × 1/2 = 1/6
19. 1/3 × 1/2 × 1/2 = 1/12
20. 2/3 ×1/2 × 1 = 1/3
21. 1/2 × 1/4 × 1/3 = 1/24
22. 1/2 × 3/4 × 2/3 = 1/4
( I guess u know how to construct the tree diagram , so I will leave this diagram to u bcuz I couldn't construct it through typing method : ) )
