Can you check my answers please? Thank you

Question

Ben is greeting customers at a music store. Of the first 20 people he sees enter the store, 9 are wearing jackets and 11 are not. What is the experimental probability that the next person to enter the store will be wearing a jacket? Enter your answer as a simplified fraction.

The experimental probability that the next person to enter the store will be wearing a jacket is 9/40. Correct?

Matt's house number is a two-digit number. Neither of the digits is 0 and the house number is even. What is the probability that Matt's house number is 18?
1/36 probability.

Philip rolls a number cube 12 times. Which is the best prediction for the number of times that he will roll a number that is odd and less than 5?
4 times.

Answer 1

1st:
Where did you get the denominator of 40 from, isn't it 9/20 ??

2nd:
correct

3rd:
prob(odd and less than five)
= 2/6 = 1/3
so out of 12 tries,
(1/3)12 = 4

correct

Answer 2

Philip rolls a number cube 12 times. Which is the best prediction for the number of times that he will roll a number that is odd and less than 5?

Answer 3

Jason, Erik, and Jamie are friends in art class. The teacher randomly chooses 2 of the 21 students in the class to work together on a project. What is the probability that two of these three friends will be chosen?