a) $\left(6,7+5,75\right):\left(-0,15\right)=12,45:\left(-0,15\right)=1245:\left(-15\right)=-83$  

b) $-9\cdot 4,7+1,2:0,3=-42,3+12:3=-42,3+4=-38,3$

c) $\left(-60-24,4\right):10=\left(-84,4\right):10=-8,44$  

d) $\left(\frac{3}{20}-\frac{1}{4}\cdot \frac{2}{5}\right):\left(\frac{1}{5}+\frac{1}{2}\right)=\left(\frac{3}{20}-\frac{2}{20}\right):\left(\frac{2}{10}+\frac{5}{10}\right)=\frac{1}{20}:\frac{7}{10}=\frac{1}{20}\cdot \frac{10}{7}=\frac{10}{140}=\frac{1}{14}$  

e) $5,43:\left(-0,6\right)+9,25=54,3:\left(-6\right)+9,25=-9,05+9,25=0,20$

f) $8\frac{2}{5}-7,8:\left(-1\frac{1}{5}\right)=8\frac{4}{10}-7,8:\left(-1\frac{2}{10}\right)=8,4-7,8:\left(-1,2\right)=8,4-\frac{78}{-12}=8,4-\left(-6,5\right)=8,4+6,5=14,9$