Why is 21 over 30 bigger than 2 over 3?

Which of the following are accepted without proof in a logical system? check all that apply.

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?

Aramp rises 4 feet over a distance of 10 feet. what is the length of the ramp?