To celebrate its 125th anniversary, a company produced 125 expensive teddy bears. these "125 karat teddy bears" are made of gold thread and have diamonds for eyes. the tables shows the approximate cost of different numbers of these bears. write an equation that can be used to find c, the cost of n bears.

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?