Hey!
--------------------------------------------------
Steps To Solve:
Slope Formula:

~Substitute with the coordinates given

~Simplify

Now we can solve for r.
~Simplify the equation.
r + 6 = -4
~Subtract 6 to both sides
r + 6 - 6 = -4 - 6
~Simplify
r = -10
--------------------------------------------------
Hence, the value of r is

--------------------------------------------------
Hope This Helped! Good Luck!