Answer: There is 14.5 miles run by Matthew in week 3.
Explanation:
Since we have given that
Week Number of miles
1 12.5
2 13.5
First we will find the slope :
(1,12.5) and (2,13.5)
So, Slope would be

So, equation of line would be

We need to find the number of miles in week 3.
So, we put x = 3,

Hence, there is 14.5 miles run by Matthew in week 3.