Please help me with this question

Jeffery conducted a survey in his school and found that 30 of the 50 eighth grade students' favorite subject is mathematics. based on the results, jeffery concluded that out of the 200 students in his school, 120 students' favorite subject is mathematics. select the statement that is true about jeffery's conclusion. a. jeffery's conclusion is not valid because the sample was biased since only 200 students were surveyed. b. jeffery's conclusion is valid because the sample was random since all of the students were eighth grade students. c. jeffery's conclusion is valid because the sample was random. d. jeffery's conclusion is not valid because the sample was biased since all of the students were eighth grade students.

Aprofessional hockey team has noticed that, over the past several seasons, as the number of wins increases, the total number of hot dogs sold at the concession stands increases. the hockey team concludes that winning makes people crave hot dogs. what is wrong with the hockey team's conclusion? a) it does not take into account the attendance during each season. b) it does not take into account the number of hamburgers sold during each season. c) it does not take into account the number of concession stands in the hockey arena. d) it does not take into account the number of seasons the hockey team has been in existence.

Astudent draws two parabolas both parabolas cross the x axis at (-4,0) and (6,0) the y intercept of the first parabolas is (0,-12). the y intercept of the second parabola is (0,-24) what is the positive difference between the a values for the two functions that describe the parabolas