7 and 8/9 is 71/9 as a mixed number
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
Given A = {a, e, i, o, u} and B = {a, l, g, e, b, r}, find A ∪ B.
harkovskaia [24]
Ahh..this is sets topics - A U B = all the elements found in A and B. But do note, do not repeat the elements if it is the same. And if the question were to ask : n(AUB) = total number of elements found in A and B.
<h2>SOLVING</h2>

What is the slope of the line passing through the point (1,2) and (5,4)

Formula used, here 
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| simplify
| reduce




