For this case we have by definition, that the equation of a line in the slope-intersection form is given by:

Where:
m: It's the slope
b: It is the cutoff point with the y axis
We need two points through which the line passes to find the slope:

We found the slope:

So, the equation is of the form:

We substitute a point to find "b":

Finally, the equation is:

Answer:
Option C
What do you need help with? it helps us to know the question!
I believe the next one would be 13.2 because if you add 8.4 to -6.4 it gets 4.8 so you just do the same thing