Please help me! I have a few of these questions, and if you can explain it it will help me ALOT.

In what form is the following linear equation written y=9x+2

17 in long 1.3 ft wide and 8in high what is the volume

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?