Devin has started a lawn care service. he will charge a mowing fee of $7 plus $2 per square yard of lawn. he also offers trimming service, at $5 plus $1 per yard of the perimeter. using x for the length of the lawn and y for the width of the lawn, which part of the expression 7 + 2xy + 5 + (2x + 2y) represents the charge for the mowing?

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?