Answer:
5 mph
Step-by-step explanation:
we have
------> equation 
------> equation 
Multiply by
the equation 
------> equation 
Sum equation
and equation 

Substitute the value of x in the equation 

therefore
the answer is the option B

$80.00 × 30%
= $24
= $80 - $24
= $56 × 7%
= $3.92
= $56 + $3.92
= $59.92
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