Remember that $\displaystyle{2.5}={2.500}\usepackage{cmbright}\Huge\$ . Now compare the digits of 2.517 and 2.500. The digits in the ones and tenths place are the same. Comparing the digits in the hundredths place, $\displaystyle{1}>{0}\usepackage{cmbright}\Huge\$ . Therefore, $\displaystyle{2.517}>{2.500}\usepackage{cmbright}\Huge\$ .