Since 7 is not a perfect square, $\displaystyle\sqrt{{7}}\usepackage{cmbright}\Huge\$ is irrational or not rational. All whole numbers are rational, so $\displaystyle\sqrt{{7}}\usepackage{cmbright}\Huge\$ cannot be a whole number, either. The correct answer is $\displaystyle\sqrt{{{7}}}\usepackage{cmbright}\Huge\$ belongs to the set of irrational and real numbers.