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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.

2. there are 250 students in a school auditorium. use numbers from the box to complete the table. 16, 38, 18, 45, 25, 50, 32, 60 grade number percent of all students of students fifth 24 sixth 95 seventh 20 eight 45

Simplify. (-3ab^3)^4 a. -7ab^12 b. -12a^4b^7 c. -81a^4b^7 d. 81a^4b^12