Answer:
1) 
2) 
3) 
Step-by-step explanation:
Given : Mr. and Mrs. Romero are expecting triplets. Suppose the chance of each child being a boy is 50% and of being a girl is 50%.
To  Find : The probability of each event.  
1) P(at least one boy and one girl)
2) P(two boys and one girl)
3) P(at least two girls)        
Solution : 
Let's represent a boy with B and a girl with G
Mr. and Mrs. Romero are expecting triplets. 
The possibility of having triplet is 
BBB, BBG, BGB, BGG, GBB, GBG, GGB, GGG
Total outcome = 8

1) P(at least one boy and one girl)
Favorable outcome =  BBG, BGB, BGG, GBB, GBG, GGB=6


2) P(at least one boy and one girl)
Favorable outcome =  BBG, BGB, GBB=3

3) P(at least two girls)
Favorable outcome = BGG, GBG, GGB, GGG=4

