200 students in a high school senior class are surveyed about what majors they intend to declare in college. Of the 200 students, 80 plan to major in mathematics, 100 plan to major in computer science, and 30 plan to pursue a double major in mathematics and computer science. Using this information, answer each of the following questions. Let MMM be the event that a randomly selected student plans to major in mathematics and CCC be the event that a randomly selected student plans to major in computer science.

Khan academy adding probabilities