The duration of routine operations at chicago general hospital has approximately a normal distribution with an average of 130 minutes and a standard deviation of 12 minutes. what proportion of operations last at least 120 minutes

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.

Solve x+3y=6 and 4x-6y=6 by elimination . show work !

Asystem of linear equations contains two equations with the same slope. select all of the correct statements. i a. the system may have two solutions. - b. the system may have infinitely many solutions. c. the system may have one solution. o d. the system may have no solution. submit