Answer:
a)

b)

c)

Explanation:
Sample space for the given case is:
S: {BBB, BBG, BGB, GBB, BGG, GBG, GGB, GGG}
n(S) = 8
where B is boy and G is girl and the position stands for first, second and third respectively.
Formula:
a) probability of exactly 3 girls
C = {GGG}

b) probability of exactly 2 boys out of three children
C: { BBG, BGB, GBB}

c) probability of exactly 0 boys out of three children
C = {GGG}
