Which expression has a positive value?

(-5)(-9)

2-4

12\(-4)

-3+(-7)

One integer is 5 more than another. their product is 104. find the integers

I'm confused on this could anyone me and show me what i need to do to solve it.

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?