\[\boxed{\mathbf{2.}\mathbf{141}}\]
\[\textbf{а)}\ \frac{120}{224} = \frac{8 \cdot 15}{8 \cdot 28} = \frac{15}{28}\]
\[\textbf{б)}\ \frac{264}{1540} = \frac{6 \cdot 44}{35 \cdot 44} = \frac{6}{35}\]
\[\textbf{в)}\ \frac{4050}{486} = \frac{162 \cdot 25}{162 \cdot 3} = \frac{25}{3}\]
\[\textbf{г)}\ \frac{4455}{4725} = \frac{135 \cdot 33}{135 \cdot 35} = \frac{33}{35}\]