What's the slope of the points (2,2) and (-2, -4)?

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?

Precalculus question, image attached.

The difference of three and the reciprocal of a number is equal to the quotient of 20 and the number. find the number.