Help me plz

Name each raycalculation tip: in ray "ab", a is the endpoint of the ray.

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 the tip varies directly with the number of guest which equation represents between the tip,t, and the number of guest,g?