Please can someone help on this ive never attempted or understand this sort of question Q = 1/6 p^2

p=13.6 correct to 3 significant figures

By considering bounds work out the value q to a suitable degree of accuracy GIVE A REASON FOR YOUR ANSWER

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?