\[\boxed{\mathbf{6.13}}\]
\[2,25 \cdot \frac{4}{9} = 2\frac{1}{4} \cdot \frac{4}{9} = \frac{9}{4} \cdot \frac{4}{9} = 1\]
\[2,25\ :2\frac{1}{4} = 2,25\ :2,25 = 1\]
\[1 - 1 = 0\]
\[0 \cdot 5,7 = 0\]
\[3,25 \cdot \frac{4}{13} = 3\frac{1}{4} \cdot \frac{4}{13} = \frac{13}{4} \cdot \frac{4}{13} = 1\]
\[3,25\ :3\frac{1}{4} = 3,25\ :3,25 = 1\]
\[1 - 1 = 0\]
\[0 \cdot 9,3 = 0\]