Đáp án:
$\dfrac{606}{1147}$
Giải thích các bước giải:
$\left (\dfrac{7}{30}.\dfrac{12}{37}+\dfrac{12}{30}.\dfrac{23}{37} \right ).\dfrac{13}{31}-\dfrac{-25}{37}.\dfrac{18}{31}\\
=\dfrac{12}{30}.\left (\dfrac{7}{37}+\dfrac{23}{37} \right ).\dfrac{13}{31}-\dfrac{-25}{37}.\dfrac{18}{31}\\
=\dfrac{12}{30}.\dfrac{13}{31}.\dfrac{30}{37}+\dfrac{25}{37}.\dfrac{18}{31}\\
=\dfrac{12.13}{31.37}+\dfrac{25.18}{37.31}\\
=\dfrac{1}{31.37}.(12.13+25.18)\\
=\dfrac{606}{1147}$
