Đáp án:
$\dfrac{2}{3}$ $-$ $\left ( \ {\dfrac{-5}{7}}\right)$ $+ \dfrac{2}{3} = \dfrac{43}{21}$
Giải thích các bước giải:
$\dfrac{2}{3}$ $-$ $\left ( \ {\dfrac{-5}{7}}\right)$ $+ \dfrac{2}{3}$
$=\dfrac{2}{3} + \dfrac{5}{7} + \dfrac{2}{3}$
$= \left ( \ {\dfrac{2}{3}+\dfrac{2}{3}}\right) + \dfrac{5}{7}$
$= \dfrac{4}{3} + \dfrac{5}{7}$
$= \dfrac{28}{21} + \dfrac{15}{21}$
$= \dfrac{28+15}{21}$
$= \dfrac{43}{21}$
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