A= (6- 2$\frac{4}{5}$ )3.$\frac{1}{8}$ – 1$\frac{3}{5}$ : $\frac{1}{4}$  B= ($\frac{-5}{4}$ – $\frac{-3}{4}$ + 7/12) : 20% – $\frac{1}{5}$ 

$A=(6-2\dfrac{4}{5})^3.\dfrac{1}{8}-1\dfrac{3}{5}:\dfrac{1}{4}$

$A=(6-\dfrac{14}{5})^3.\dfrac{1}{8}-\dfrac{8}{5}.4$

$A=(\dfrac{16}{5})^3.\dfrac{1}{8}-\dfrac{32}{5}$

$A=\dfrac{4096}{125}.\dfrac{1}{8}-\dfrac{32}{5}$

$A=\dfrac{512}{125}-\dfrac{32}{5}$

$A=\dfrac{512}{125}-\dfrac{800}{125}$

$A=\dfrac{-288}{125}$

$B=(\dfrac{-5}{4}-\dfrac{-3}{4}+\dfrac{7}{12}):20\%-\dfrac{1}{5}$

$B=(\dfrac{-15}{12}-\dfrac{-9}{12}+\dfrac{7}{12}):\dfrac{20}{100}-\dfrac{1}{5}$

$B=\dfrac{1}{12}.\dfrac{100}{20}-\dfrac{1}{5}$

$B=\dfrac{1}{12}.5-\dfrac{1}{5}$

$B=\dfrac{5}{12}-\dfrac{1}{5}$

$B=\dfrac{13}{60}$