Correct. The number $\displaystyle{3}\sqrt{{{7}}}\usepackage{cmbright}\Huge\$ is irrational because it cannot be represented as a fraction; it is a non-repeating and non-terminating decimal. The decimal $\displaystyle{0.3}{\overline{{{3}}}}\usepackage{cmbright}\Huge\$ can be written as the fraction $\displaystyle\frac{{1}}{{3}}\usepackage{cmbright}\Huge\$ , so it is rational. The set of real numbers includes all rational and irrational numbers.