First off, nicely done on the exponents. You'd be surprised on how bad some look ,:D
a)

b)
Biased, because there is only survey of one group of people (one grade, one class). The sample (the class) is too small compared to the population (assuming it’s an average school size). You will end up with less than 1 percent of the population size thus the survey is not reliable information.
Answer:
3?
Step-by-step explanation:
im not 100% sure
4 1/2(2)=9. Multiply by 2 to get total
9- 3 1/2=z. Subtract 3 1/2 from total to get Z
5 1/2= Z