\[\boxed{\mathbf{2.537}}\]
\[1)\ 1\frac{1}{4}\ :2\frac{1}{4} \cdot 1\frac{2}{7} = \frac{5}{4}\ :\frac{9}{4} \cdot \frac{9}{7} =\]
\[= \frac{5 \cdot 4 \cdot 9}{4 \cdot 9 \cdot 7} = \frac{5}{7}\]
\[2)\ 4\frac{1}{3} \cdot 1\frac{7}{8}\ :\frac{13}{15} = \frac{13}{3} \cdot \frac{15}{8} \cdot \frac{15}{13} =\]
\[= \frac{13 \cdot 15 \cdot 15}{3 \cdot 8 \cdot 13} = \frac{5 \cdot 15}{8} = \frac{75}{8} =\]
\[= 9\frac{3}{8}\]
\[3)\ 1\frac{3}{7} \cdot \frac{11}{15}\ :4\frac{5}{7} = \frac{10}{7} \cdot \frac{11}{15}\ :\frac{33}{7} =\]
\[= \frac{10 \cdot 11 \cdot 7}{7 \cdot 15 \cdot 33} = \frac{2}{3 \cdot 3} = \frac{2}{9}\]
\[4)\ 1\frac{6}{7}\ :3\frac{5}{7} \cdot \frac{4}{9} = \frac{13}{7}\ :\frac{26}{7} \cdot \frac{4}{9} =\]
\[= \frac{13 \cdot 7 \cdot 4}{7 \cdot 26 \cdot 9} = \frac{4}{2 \cdot 9} = \frac{2}{9}\]