Đáp án:
Giải thích các bước giải:
cách 1:
$S=-\dfrac{5}{9}+\dfrac{7}{12}+\dfrac{5}{9}-\dfrac{5}{12}$
$=(-\dfrac{5}{9}+\dfrac{5}{9})+(\dfrac{7}{12}-\dfrac{5}{12})$
$=\dfrac{2}{12}=\dfrac{1}{6}$
cách 2:
$S=-\dfrac{5}{9}+\dfrac{7}{12}+\dfrac{5}{9}-\dfrac{5}{12}$
$=(-\dfrac{5}{9}+\dfrac{7}{12})+(\dfrac{5}{9}-\dfrac{5}{12})$
$=\dfrac{1}{36}+\dfrac{5}{36}$
$=\dfrac{1}{6}$