Which number is greatest? 2.89 times 10 Superscript negative 8 1.997 times 10 Superscript 2 8.9 times 10 Superscript negative 6 5 times 10 Superscript negative 6

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

Last month, a 770 g box of cereal was sold at a grocery store for $3.10. however, this month, the cereal manufacturer launched the same cereal in a 640 g box, which is being sold at $2.50. what is the percent change in the unit price?

Put the equation in slope intercept form by solving for y