Pls help 25 points

find the value
and pls explain h

Twenty-five percent of the customers entering a grocery store between 5 p.m. and 7 p.m. use an express checkout. consider five randomly selected customers, and let x denote the number among the five who use the express checkout.

Let f(x) = 3 − x . find the average rate of change of f(x) from x = a to x = a + h and simplify your answer so that no single factor of h is left in the denominator.

: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?