a drawer contains one pair of brown socks and one
pair of white socks. the table shows the possible
outcomes, or sample space, for choosing a sock,
replacing it, and then choosing another sock.
if the first sock is not replaced, how many possible
outcomes are there?
how many of these outcomes contain a matching pair
of socks?

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?