for each of the equations, determine the change in the number of moles of gas, δgas . (nh4)2co3(s)⟶2nh3(g)+co2(g)+h2o(g)

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)?