Use the empirical rule to solve the problem. the systolic blood pressure of 18-year-old women is normally distributed with a mean of 120 mmhg and a standard deviation of 12 mmhg. what percentage of 18-year-old women have a systolic blood pressure between 96 mmhg and 144 mmhg

First you need to determine how much standard deviation the range is. 
120+12*x= 96
x= 96-120/ 12= -2

120+12*y=144
y= 144-120/12= +2

Systolic blood pressure between 96 mmHg and 144 mmHg means that the blood pressure is at -2SD to +2SD. The Z-score for -2SD is 0.0228 and +2SD is 0.9772
So the percentage would be: 0.9772- 0.0228  * 100%= 95.44%