Constructing a linear model

Question

Suppose you are the new owner of a fruit stand and on your first day of selling fruit, you sell five apples. assume that, for the next 20 days, the amount of apples you sell increases by one every two days. Construct a linear function which models this situation. Assuming that this model is valid for the next 30 days, how many apples should you expect to sell on day 27?

Answer 1

This is a linear model which goes through (1, 5) and (3, 7) where x = day # and y = apples sold 

The slope of the line is 1: (7 - 5)/(3 - 1)

 

The equation then is 1 = (y-5)/(x-1)  => y = x + 4

 

When x=27,  y=31