The mean systolic blood pressure of adult males is normally distributed with a mean of 138 (millimeters of mercury) and a standard deviation of 9.7. What percent of adult males have blood pressure between 161.28 and 164.9?

Math is absolutely my weakest subject, and I am very lost... there is a chart for one example in our text..but I am not sure if I should use the chart to get the percentages or if there is some way to figure them that I am missing. This is what I have so far...

161.28 - 138/9.7=23.28/9.7= 2.4

164.9-138/9.7=26.9/9.7=2.77

--- I know that these are the z-scores, so how do I get the percentages from this? I know that I will have to subtract the percentages to get the answer...but I am lost on how to find the percentages...Can anyone please help!!??