\[- 2,86 \cdot \frac{6}{7} - \frac{6}{7} \cdot 0,64 =\]
\[= \frac{6}{7} \cdot ( - 2,86 - 0,64) =\]
\[= \frac{6}{7} \cdot ( - 3,5) = - \frac{6}{7} \cdot \frac{7}{2} = - 3.\]