Originally Posted by

**peanutbutter** I'm still working with:

"A region's population is 7,800, per capita income approximately observes normal distribution with mean $12,100 and standard deviation $6,050."

Above what income level in dollars do the richest 5% of the region's population earn?

So since 0.4500 is between 1.64 and 1.65 in my table, I choose 1.645 to be my z-score. ( I still don't understand why this is?)

0.4500 = 1.645

1.645=(X-12100) / 6050

9952.25= X - 12100

X= 22052.25

I feel this is the right answer, but for some reason I can't ever figure out the proper notations to include in my problem solving process so that I get full marks. If I just write down what I did up there, is that "proper"?