The mean price of purchases is $110 and the standard deviation = $12. What is the probability of a purchase exceeding $90?

I need help reviewing. Please give some input.

Find your Z score = (x - μ)/SD, where x = desired value, μ = mean, and SD = standard deviation.

Look up this Z score in the table in the back ofyour statistics text labeled something like "areas under the normal distribution." You can decide which proportion answers your question.

I hope this helps. Thanks for asking.