Which statement must be true to prove m∠1 + m∠2 + m∠3 = 180?.

On a test the graders have a mean of 77 and a standard deviation of 8. if we can approximate the distribution of these graders by a number distribution what percent of the students. a) scores higher than 77? b) should pass the test (grades > 60)? c) should fail the test (grades < 60)?