Before multiplying, reorder the denominators and cancel the common factor. $\displaystyle\frac{{{3}\cdot{4}}}{{{4}\cdot{5}}}=\frac{{{3}\cdot{4}}}{{{5}\cdot{4}}}=\frac{{{3}\cdot{1}}}{{{5}\cdot{1}}}=\frac{{3}}{{5}}\usepackage{cmbright}\Huge\$