Answer:
The Answer is;
No, it is not a valid inference because his classmates do not make up a random sample of the students in the school.
Step-by-step explanation:
You cannot make a valid inference of the preference of watching TV talk shows by only considering students in one class. You have to randomly select people from the whole population (i.e the total number of students in the school) and then make an inference.
Answer:

Step-by-step explanation:
Given
See attachment for ski trails
Required
Total length of
ski trails
From the attached figure, there are 3 skis with length 
So:
The total length is:

Express fraction as improper fraction




566,000,000
standard notation just means write the number out insted of in an equasion