Answer:
Option C. 
Step-by-step explanation:
we know that
In the rectangle of the figure

so

The constant is equal to 
Clara forgot to distribute the - sign to- (2b-r) through all the terms the answer would be 6b+3r
We know form our problem that the third day she biked 20 miles, so we have the point (3,20). We also know that <span>on the eighth day she biked 35 miles, so our second point is (8,35).
To relate our two point we are going to use the slope formula: </span>

We can infer form our points that

,

,

, and

. so lets replace those values in our slope formula:



Now that we have the slope, we can use the point-slope formula <span>determine the equation of the line that best fit the set for Maggie’s data.
Point-slope formula: </span>




We can conclude that the equation of the line that best fit the set for Maggie’s data is

.