Đáp án+Giải thích các bước giải:

a)

$\text{(− $\dfrac{9}{15}$) ⋅ $\dfrac{7}{3}$ ⋅ ($\dfrac{25}{9}$) ⋅ 81}$

$\text{= − $\dfrac{9 ⋅ 7 ⋅ 25 ⋅ 81}{15 ⋅ 3 ⋅ 9}$}$ 

$\text{= − $\dfrac{9 ⋅ 7 ⋅ 5 ⋅ 5 ⋅ 3 ⋅ 3 ⋅ 9}{3 ⋅ 5 ⋅ 3 ⋅ 9}$}$ 

$\text{= − $\dfrac{7 ⋅ 5 ⋅ 9}{1}$}$ 

$\text{= 35 ⋅ 9}$

$\text{= 315}$

$\text{b)}$

$\text{$\dfrac{6}{13}$ ⋅ $\dfrac{1}{4}$ − $\dfrac{14}{26}$ ⋅ $\dfrac{1}{4}$}$

$\text{= $\dfrac{1}{4}$ ⋅ ($\dfrac{6}{13}$ − $\dfrac{14}{26}$)}$

$\text{= $\dfrac{1}{4}$ ⋅ ($\dfrac{6}{13}$ − $\dfrac{7}{13}$)}$

$\text{= $\dfrac{1}{4}$ ⋅ $\dfrac{1}{13}$}$

$\text{= $\dfrac{1}{52}$}$

$\text{c)}$

$\text{(1$\dfrac{4}{5}$ ⋅ $\dfrac{12}{13}$ ⋅ $\dfrac{10}{36}$) : (− $\dfrac{6}{13}$)}$

= $\text{($\dfrac{9}{5}$ ⋅ $\dfrac{12}{13}$ ⋅ $\dfrac{10}{36}$) ⋅ (− $\dfrac{13}{6}$)}$

= $\text{− $\dfrac{9 ⋅ 12 ⋅ 10 ⋅ 13}{5 ⋅ 13 ⋅ 36 ⋅ 6}$}$

= $\text{− $\dfrac{3 ⋅ 3 ⋅ 12 ⋅ 2 ⋅ 5 ⋅ 13}{5 ⋅ 13 ⋅ 12 ⋅ 3 ⋅ 2 ⋅ 3}$}$

= $\text{1}$