Incorrect.

Direct variation: As one quantity rises, so does the other at a constant rate. This can be represented by: $\displaystyle{y}={k}{x}\usepackage{cmbright}\Huge\$

Inverse variation: As one quantity increases, the other quantity decreases. This can be represented by: $\displaystyle{y}=\frac{{k}}{{x}}\usepackage{cmbright}\Huge\$

Joint variation: More than two quantities are needed. This can be represented by: $\displaystyle{y}={k}{x}{z}\usepackage{cmbright}\Huge\$