Substitute the slope 4 into $\displaystyle{y}={m}{x}+{b}\usepackage{cmbright}\Huge\$ : $\displaystyle{y}={4}{x}+{b}\usepackage{cmbright}\Huge\$

Substitute the coordinates of the point (8, 5) for x and y: $\displaystyle{5}={4}{\left({8}\right)}+{b}\usepackage{cmbright}\Huge\$

Solve for b: $\displaystyle{5}={32}+{b}\usepackage{cmbright}\Huge\$ , so $\displaystyle-{27}={b}\usepackage{cmbright}\Huge\$

Rewrite $\displaystyle{y}={m}{x}+{b}\usepackage{cmbright}\Huge\$ with $\displaystyle{m}={4}\usepackage{cmbright}\Huge\$ and $\displaystyle{b}=-{27}\usepackage{cmbright}\Huge\$ : $\displaystyle{y}={4}{x}-{27}\usepackage{cmbright}\Huge\$