I need help for my exam ?

At the newest animated movie, for every 9 children, there are 4 adults. there are a total of 39 children and adults at the movie.

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?

Tom drove 206 miles in 3.9 hours. estimate his average speed.