Correct. Solve for y, so that the equation is in the form $\displaystyle{y}={m}{x}+{b}\usepackage{cmbright}\Huge\$ .

Subtract $\displaystyle{12}{x}\usepackage{cmbright}\Huge\$ from both sides: $\displaystyle{3}{y}={15}-{12}{x}\usepackage{cmbright}\Huge\$

Divide both sides by 3: $\displaystyle{y}={5}-{4}{x}\usepackage{cmbright}\Huge\$ or $\displaystyle{y}=-{4}{x}+{5}\usepackage{cmbright}\Huge\$

The line has a slope of $\displaystyle-{4}\usepackage{cmbright}\Huge\$ . A line parallel to it will have the same slope of $\displaystyle-{4}\usepackage{cmbright}\Huge\$ .