\[5\frac{25}{28} \cdot \frac{4}{45} - \frac{5}{39} = \frac{165 \cdot 4}{28 \cdot 45} - \frac{5}{39} =\]
\[= \frac{11^{\backslash 13}}{7 \cdot 3} - \frac{5^{\backslash 7}}{13 \cdot 3} = \frac{143 - 35}{273} =\]
\[= \frac{108}{273} = \frac{36}{91}.\]