I need help with my statistics problem

Question

The average charitable contribution itemized per tax return in Pennsylvania is? $792 with a standard deviation of? $103. Find the limit for the upper? 30% of contributions. Assume a normal distribution.

Answer 1

792=mean. sd=103 dollars

what is the cut off for the top 30%??

z score for .30 = .38209

= (x -mean)/sd = x -792)/103

x = 792 + 103(.38209=792+39.36

= $831.36 separates top 30% from bottom 70%