What is "write the equation if you had 400 friends on facebook and defriended 20 people per day. let y be the number of friends and x the number of days." plz

The table shows the balance of a money market account over time. write a function that represents the balance y (in dollars) after t years.

The volume of the sun is approximately 1 × 10^18 cu km, while the volume of jupiter is approximately 1 × 10^15 cu km. which of the following is true? a. the volume of jupiter is approximately one thousand times the volume of the sun. b. the volume of jupiter is approximately one hundred times the volume of the sun. c. the volume of the sun is approximately one thousand times the volume of jupiter. d. the volume of the sun is approximately one hundred times the volume of jupiter.

Can someone show me step by step how to do this?