The ages of students in a school are normally distributed with a mean of 15 years and a standard deviation of 2 years. approximately what percent of the students are between 14 and 18 years old?

a. 24.17%

b. 62.47%

c. 30.85%

d. 93.32%

i've tried solving this, and i ended up with z-scores -0.5 for 14-year-olds and 1.5 for 18-year-olds. and i also matched them using a chart and got "0.3085" and "0.9332", but i don't know if i should add or subtract because, in a similar problem i had to add but if i add the percentages, it exceed 100%. i am confused;