Đáp án + Giải thích các bước giải:
a)
$\dfrac{3}{7} . \dfrac{5}{8} +\dfrac{3}{7} . \dfrac{11}{8} - \dfrac{3}{7}\\$
$=\dfrac{3}{7} . \dfrac{5}{8} + \dfrac{3}{7} . \dfrac{11}{8} - \dfrac{3}{7} . 1\\$
$=\dfrac{3}{7} . \bigg(\dfrac{5}{8} + \dfrac{11}{8} - 1\bigg)\\$
$=\dfrac{3}{7} . 1\\$
$=\dfrac{3}{7}$
b)
$\dfrac{17}{14} : \bigg|\dfrac{-34}{21}\bigg| + \dfrac{1}{5} - \dfrac{3}{4}$
$=\dfrac{17}{14} . \dfrac{21}{34} + \dfrac{1}{5} - \dfrac{3}{4}$
$=\dfrac{3}{4} + \dfrac{1}{5} - \dfrac{3}{4}$
$=\bigg(\dfrac{3}{4} - \dfrac{3}{4}\bigg) + \dfrac{1}{5}$
$=0 + \dfrac{1}{5}$
$= \dfrac{1}{5}$
