I'm new here. I have a problem that I've been working on for a few hours that I just can't seem to figure out. I decided to work the example in the book, but I'm having a problem determining where to get it and how the z-value is applied. So far I've worked out my bell curve, but don't know where to go from there. Here's the problem.

Professor Mann has determined that the scores in his statistics course are approximately normally distributed with a mean of 72 and a standard deviation of 5. He announces to the class that the top 15 percent of the scores will earn an A. What is the lowest score a student can earn and still receive an A?

The book says - The z-value associated corresponding to 35 percent is about 1.04. Where does this come from???

The formula then becomes 1.04=x-72/5 then

X = 72 + 1.04(5) = 72 + 5.5 = 77.2

I saw the link from another post that displays a z table, but it does not go up to 35, so should my problem go beyond the table is there a formula for figuring the z-value?

Thanks in advance!!