if you notice in the graph, you can pick any two points to get the slope of it, hmm let's say we use 0, -3 and 6,1, which are there in the picture,
[tex]\bf \begin{array}{ccccccccc}
&&x_1&&y_1&&x_2&&y_2\\
% (a,b)
&&(~ 0 &,& -3~)
% (c,d)
&&(~ 6 &,& 1~)
\end{array}
\\\\\\
% slope = m
slope = m\implies
\cfrac{\stackrel{rise}{ y_2- y_1}}{\stackrel{run}{ x_2- x_1}}\implies \cfrac{1-(-3)}{6-0}\implies \cfrac{1+3}{6-0}\implies \cfrac{4}{6}\implies \cfrac{2}{3}[/tex]
