Step-by-step explanation:
out of the 21 students, 8 do not play neither basketball nor baseball.
so, 13 students play at least one of these games.
10 play basketball, and 9 play baseball. that would be 19 together. but we have only 13 players.
that means 6 students (19 - 13) must play both games.
remember, a probability is always
desired cases / possible cases
so, when we are looking for the students, who play both games, we have 6 desired cases out of a total of 21.
and the probability to pick one of them is therefore
6/21 = 2/7 = 0.285714286...
