Giải thích các bước giải:
a.$\dfrac{-3}{7}\cdot\dfrac25+\dfrac25\cdot (-\dfrac5{14})-\dfrac{18}{35}$
$=\dfrac{-3}{7}\cdot\dfrac25-\dfrac25\cdot \dfrac5{14}-\dfrac{18}{35}$
$=\dfrac{-6}{35}-\dfrac{5}{35}-\dfrac{18}{35}$
$=\dfrac{-6-5-18}{35}$
$=\dfrac{-29}{35}$
b.Ta có:
$(\dfrac23-\dfrac5{11}+\dfrac14):(1+\dfrac5{12}-\dfrac7{11})$
$=(\dfrac{88}{132}-\dfrac{60}{132}+\dfrac{33}{132}):(\dfrac{17}{12}-\dfrac{7}{11})$
$=\dfrac{88-60+33}{132}:\dfrac{187}{132}-\dfrac{84}{132}$
$=\dfrac{61}{132}:\dfrac{103}{132}$
$=\dfrac{61}{132}\cdot\dfrac{132}{103}$
$=\dfrac{61}{103}$
c.$(13.6-37.8)\cdot (-3.2)$
$=(-24.2)\cdot (-3.2)$
$=24.2\cdot 3.2$
$=77.44$
d.$(-25.4)\cdot (18.5+43.6-16.8):12.7$
$=(-25.4)\cdot (62.1-16.8):12.7$
$=(-25.4)\cdot45.3:12.7$
$=-25.4\cdot45.3:12.7$
$=-1150.62:12.7$
$=-90.6$