The students council is asking people to donate money for the new park outside the school. everyone who makes the suggested donations amount will be given a bracelet. if everyone donates the suggested amount, b bracelets are given away, what algebraic expression represents the total amount collected in donations

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?