Question 970850
What's the probability he WON'T make a sale?

That's easier, because he could make 1,2,or 3 sales, and each has its own probability.

Probability he will NOT sell is
0.4*0.4*0.4=0.064

Probability he will sell to at least one is 0.936   (1-0.064).

In statistics problems with multiple choices, sometimes it is easier to figure out what you DON'T want and subtract it from 1.