How many square feet are in a square mile?

What is the distance between the points (2 -3) and (-6 4) on the coordinate plane

Evaluate the expression for the given value of the variable 2×(c2-5) for c=4

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?