I assume he must choose to draw 3 different figures out of 10. I assume that he can choose any figure, solid or plane, so his first choice is 1/10, second choice is 1/9, third choice is 1/8. The outcome of a pyramid, cylinder and hexagon has a probability of 1/10×1/9×1/8 and any arrangement of three is 6, so the probability is 6(1/10)(1/9)(1/8)=1/120.