How do you find the equation of a line given with two points?

What are the coordinates of the midpoint of ab? ,1/2) /2,-1) ,-3/2) /2,-2)

Amanda went into the grocery business starting with five stores. after one year, she opened two more stores. after two years, she opened two more stores than the previous year. if amanda expands her grocery business following the same pattern, which of the following graphs represents the number of stores she will own over time?

Need plz been trying to do it for a long time and still haven’t succeeded