+57(7-2), complete the following statement:
f(3) =

How do i do this? i don’t understand

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?

Typically a point in a three dimensional cartesian coordinate system is represented by which of the following answers in the picture !