What is the equation of a line having slope $$ - \frac{1}{3}$$ and y-intercept equal to 6?

$$\eqalign{ & \left( {y - {y_1}} \right) = \left( {\frac{{{y_2} - {y_1}}}{{{x_2} - {x_1}}}} \right)\left( {x - {x_1}} \right) \cr & \Rightarrow \left( {y - 6} \right) = - \frac{1}{3} \times \left( x \right) \cr & \Rightarrow 3y - 18 = - x \cr & \Rightarrow x + 3y = 18 \cr} $$