5 times the sum of F amd 13 equala 125

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?

Is a positive integer raised to a negative power always positive

Either enter an exact answer in terms of \piπ or use 3.143.14 for \piπ and enter your answer as a decimal.