a. 5,75 . $\frac{-8}{9}$
= $\frac{23}{4}$ . $\frac{-8}{9}$
= $\frac{-46}{9}$
b. $2\frac{3}{8}$ . (-0,4)
= $\frac{19}{8}$ . $\frac{-2}{5}$
= $\frac{-19}{20}$
c. $\frac{-12}{5}$ : (-6,5)
= $\frac{-12}{5}$ : $\frac{-13}{2}$
= $\frac{-12}{5}$ . $\frac{-2}{13}$
= $\frac{24}{65}$