Does anyone know how to do the checking part? I've got everything else down but I don't know how to do the checking part.

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.

F(x) = 1/x g(x)=x-4 can you evaluate (g*f)(0) ? why or why not?

Jennifer taking a quiz and has answered 13 questions so far. if there are 25 questions on jennifer test, how many questions does she have left to answer