What is the probability that a randomly selected student will study more than three hours and earn a 71 to 90?

Answer: 0.375
Explanation
The probability can be given by:
[tex]P=\frac{\text{ desired event}}{\text{ total outcome}}[/tex]In our case, we could say that the desired event is:
[tex]P=\frac{18}{48}=\frac{3}{8}=0.375[/tex]