Answer
a) y | p(y)
25 | 0.8
100 | 0.15
300 | 0.05
E(y) = ∑ y . p(y)
E(y) = 25 × 0.8 + 100 × 0.15 + 300 × 0.05
E(y) = 50
average class size equal to E(y) = 50
b) y | p(y)
25 | 
100 | 
300 | 
E(y) = ∑ y . p(y)
E(y) = 25 × 0.4 + 100 × 0.3 + 300 × 0.3
E(y) = 130
average class size equal to E(y) = 130
c) Average Student in the class in a school = 50
Average student at the school has student = 130
53). 100 servings / 20 people = (100/20) (svngs/ppl)
= 5 servings per person.
Each person gets 1/20 = 5% = 0.05 of the pan.
54). 100 servings / 40 people = (100/40) (svngs/ppl)
= 2.5 servings per person.
Each person gets 1/40 = 2.5% = 0.025 of the pan.
55). 100 servings / 30 people = (100/30) (svngs/ppl)
= (3 and 1/3) servings per person.
Each person gets 1/30 = (3 and 1/3) % = 0.0333... of the pan.
You would have to do 15 - 2 because according to PEMDAS you do parentheses first and you would do the multiplication and division
I believe yes, no, no, no but I am not sure