The slope of the line is equal to $\displaystyle\frac{{{4}-{2}}}{{{4}-{3}}}=\frac{{2}}{{1}}={2}\usepackage{cmbright}\Huge\$ (or $\displaystyle\frac{{{2}-{4}}}{{{3}-{4}}}=\frac{{-{2}}}{{-{1}}}\usepackage{cmbright}\Huge\$ , which also equals 2).