Scott, Jessica, and Danilo played checkers with each other. Scott won 4 games and lost 2 games. Jessica won 3 games and lost 3 games. If Danilo lost 3 games, how many games did he win?

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?