Invested his savings in two investment funds. The $ 20,000 that he invested in Fund A returned a 10 % profit. The amount that he invested in Fund B returned a 3 % profit. How much did he invest in Fund B, if both funds together returned a 8 % profit?

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?