Sum of a number squared and twice the number

In the polynomial below, what number should replace the question mark to produce a difference of squares? x2 + ? x - 36

Which graph represents the parent function of y=(x+2)(x-2)

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?