Please help me, quick!

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?

If there are 3.281 feet in 1 meter, how many inches are in one centimeter

Perry observes the opposite parallel walls of a room in how many lines do the plains containing the walls intersect