University a boasts a 15: 1 student to teacher ratio whereas university b advertises having 150 professors to teach just 3,000 students. if university b wanted to adopt the same student to teacher ratio as univeristy a, would they need to hire professors, or let some go?

Each person in an it department of 25 people works on at least one of 3 major projects: system security, program implementation, platform development. 10 people work on system security, 13 work on program implementation, and 12 work on platform development. 4 people work on system security and platform development, 5 people work on program implementation and platform development, and 2 people work on all three projects. how many people work on system security and program implementation?