Đáp án:
Giải thích các bước giải:
$a)\\\dfrac{3}{4}-\dfrac{5}{6}.\bigg(\dfrac{1}{6}+\dfrac{1}{8}\bigg):\dfrac{7}{12} \\ =\dfrac{3}{4}-\dfrac{5}{6}.\dfrac{7}{24}:\dfrac{7}{12} \\ =\dfrac{3}{4}-\dfrac{35}{144}:\dfrac{7}{12}\\ =\dfrac{3}{4} - \dfrac{5}{12} =\dfrac{4}{12}=\dfrac{1}{3} \\ b)\\ \dfrac{15}{8}:\dfrac{45}{6}-\dfrac{1}{13}.\bigg(\dfrac{4}{9}-\dfrac{1}{12}\bigg) \\ =\dfrac{1}{4}-\dfrac{1}{3}.\dfrac{13}{36} = \dfrac{1}{4}-\dfrac{13}{108} \\ =\dfrac{27}{108}-\dfrac{13}{108} = \dfrac{14}{108}=\dfrac{7}{54}$
chúc bạn học tốt T^T
