This is one easy one
You have to focus on the ml
The exp prob was 1/2 times
Answer:

Step-by-step explanation:
Number of boys = 12
Number of girls = 18
Total number of students = 12 + 18 = 30
Probability refers to chances of occurrence of any event.
Probability = Number of favorable outcomes ÷ Total number of possible outcomes
To find P(Senior | Boy), use 
P(Senior and Boy) = 
P(Boy) = 
So,
P(Senior | Boy) = P(Senior and Boy) ÷ P(Boy) = 