△RST shows a city's plan for a new building near the beach that will have free surfboard rentals. Given that the area of △RST is x, complete the equation m∠T = sin–1 mn in terms of the variables x, r, s, and t.

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?