I have been keeping up in this class pretty easily up until I missed 1 class, and the class is only on Saturdays so of course I am lost even after reading the chapter. I am so sure there is a simple answer for this that I am just looking over.

z-score for a right-tail probability:
a. for the normal distribution shown below, find the z-score.

the graphic is a normal distribution (bell curve) and it has a shaded area that is .20 (20%) of the curve to the right. the graph has mu and then mu + z*sigma.

I know that I need to find the unshaded area, .80, then use the chart at the end of book. I see entries for .7995 or .8023. Am I just over thinking this? Should I just use the .8023?

Any help is appreciated