Is the number -9/20 a rational number

Agreeting card company can produce a box of cards for $7.50. if the initial investment by the company was $50,000, how many boxes of cards must be produced before the average cost per box falls to $10.50?

What set does not contain -3 the set of all real numbers the set of all integers the set of all whole numbers the set of all rational numbers

Which is greater, 7 p 5 or 7 c 5? 7p5 7c5