I will be giving 10 points please answer!!

Explain how you can use the associative property to evaluate (7x50)x4.

You are at a restaurant and owe $38 for your meal. you want to leave a 20% tip. how much will your tip be?

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?