What times what gets 6.25 but adds up to5

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?

Hello, i need compare km^2 and km. what's difference in this?

Ineed with question three. i don't understand how i'm supposed to achieve 3 marks.