Rewrite both fractions so they have a common denominator, 30. You find that $\displaystyle\frac{{20}}{{30}}<\frac{{21}}{{30}}\usepackage{cmbright}\Huge\$ , so $\displaystyle\frac{{4}}{{6}}<\frac{{7}}{{10}}\usepackage{cmbright}\Huge\$ as well.