Đáp án:
a. $\dfrac{77}{240}$
b. $\dfrac{19}{27}$
Giải thích các bước giải:
a.Ta có:
$\dfrac{19}{48}-\dfrac{3}{40}$
$=\dfrac{95}{240}-\dfrac{18}{240}$
$=\dfrac{95-18}{240}$
$=\dfrac{77}{240}$
b.Ta có:
$\dfrac16+\dfrac7{27}+\dfrac5{18}$
$=\dfrac{9}{54}+\dfrac{14}{54}+\dfrac{15}{54}$
$=\dfrac{9+14+15}{54}$
$=\dfrac{38}{54}$
$=\dfrac{19}{27}$