Give the difference of (7.2 x 10-7) - (4.5 x 10-7)

The multiplication property of zero states that the product of any number and 0 is 0. what must be true about either a or b to make ab=0

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?

Don't know how to find x given these segment lengths