What is an equivalent ratio for 12/21

If f(x) =3x-2 and g(x) =2x+1 fins (f+ g) (x)

Pls brainliest will be awarded if answer is correct

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?