Please help! Find the inverse of f(x)=(ax+b)/(cx+d) using algebraic steps. Use your results to explain why f(x)=(7x+5)/(3x-7) has its own inverse f^-1(x)=(7x+5)/(3x-7).

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?