Correct. The slope of $\displaystyle{y}={3}{x}-{4}\usepackage{cmbright}\Huge\$ is 3, so any line perpendicular to it will have slope $\displaystyle-\frac{{1}}{{3}}\usepackage{cmbright}\Huge\$ (the opposite reciprocal of 3). The equation $\displaystyle{y}+{1}=-\frac{{1}}{{3}}{\left({x}-{3}\right)}\usepackage{cmbright}\Huge\$ is the point slope form of the line with slope $\displaystyle-\frac{{1}}{{3}}\usepackage{cmbright}\Huge\$ that goes through (3, -1).