help on algebra

Question

a calculus exam that was taken by 86 students is recorded and normally distributed. The mean score on the exam is 73.5 and the standard deviation is 2.8. What percent of the scores are in the 70.7 to 79.1 range?

Answer 1

z = (x - μ)/σ

Find z-scores for x = 70.7 and 79.1 and subtract. That'll give the area under the normal curve between those two values (percent of scores in that range). σ = 2.8; μ = 73.5.