Give me an example of scale balance illustrating inequalities

The physical fitness of an athlete is often measured by how much oxygen the athlete takes in (which is recorded in milliliters per kilogram, ml/kg). the mean maximum oxygen uptake for elite athletes has been found to be 60 with a standard deviation of 7.2. assume that the distribution is approximately normal.

How do i do this activity, is appreciated

:24% of students in a class are girls. if there are less than 30 students in this class, how many students are there? how many girls are there?