b) –11,6 + 5,7 – 8,9;

b) –11,6 + 5,7 – 8,9

$$\begin{gathered} =\frac{5}{7}.\left(\frac{-2}{11}+\frac{-9}{11}+1\right) \\ =\frac{5}{7}.\left(\frac{-11}{11}+1\right) \\ =\frac{5}{7}.\left(-1+1\right) \\ =\frac{5}{7}.0 \\ =0 \end{gathered}$$