When all n teams in a league play every other team twice, a total of N games are played, where N=n2−n. A soccer league has 5 teams and all teams play each other twice. How many games are played?

In the football stadium, there are 18 empty seats out of 360 total seats. (1a) write the ratio of empty seats to total seats as a fraction in simplest form. (1b) then explain its meaning.

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?

Find the value of x for which line a is parallel to line b