Correct. The least common denominator is $\displaystyle{5}{c}\cdot{2}{d}={10}{c}{d}\usepackage{cmbright}\Huge\$ . Rewrite each fraction to have this denominator:

$\displaystyle\frac{{3}}{{{5}{c}}}-\frac{{1}}{{{2}{d}}}=\frac{{3}}{{{5}{c}}}\cdot\frac{{{2}{d}}}{{{2}{d}}}-\frac{{1}}{{{2}{d}}}\cdot\frac{{{5}{c}}}{{{5}{c}}}=\frac{{{6}{d}}}{{{10}{c}{d}}}-\frac{{{5}{c}}}{{{10}{c}{d}}}=\frac{{{6}{d}-{5}{c}}}{{{10}{c}{d}}}\usepackage{cmbright}\Huge\$