PROBABILITY
posted by JHONY .
There are 3 lucky tickets among 10 lottery tickets. 3 tickets are
drawn at random. What is a probability that one ticket selected randomly
from those three is lucky?

The probability that any particular ticket in the group of three is "lucky", is 3/10.
You could spend a lot of time calculating whether the frst group of three has 0, 1, 2 or 3 lucky tickets, but it isn't necessary. Then you'd have to add up the weighted probabilities of drawing a lucky one in each case.
When you pick one ticket from that set of three, without knowing or worrying about how many lucky ones there are in the set, its probability of being lucky remains 3/10.