Start with the point-slope formula, shown below in bold.
Y - y1 = m(x - x1)
Our point which in this case is (6, 8) represents (x1, y1) in our formula.
~Substitute
Y - 8 = -2(x - 6)
I will be writing this equation in standard form.
First distribute the -2 through the parentheses.
This gives us y - 8 = -2x + 12.
Next we would move the -8 to the right side of the equation
by adding 8 to both sides to get y = -2x + 20.
Finally we move our x term to the left side of the equation
by adding 2x to both sides and our answer is 2x + y = 20.