We sample 15 balls from the bag without replacement. What is the probability of obtaining at most 10 red balls

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?

Im so bad at fractions they are not my best math thing to work on

Convert 3,200,000 to a scientific notation.