Đáp án:
Giải thích các bước giải:
$\dfrac{7}{19}$ . $\dfrac{8}{11}$ + $\dfrac{3}{11}$ . $\dfrac{7}{19}$ + $\dfrac{-12}{19}$
= $\dfrac{7}{19}$ . ( $\dfrac{8}{11}$ + $\dfrac{3}{11}$ ) - $\dfrac{-12}{19}$
= $\dfrac{7}{19}$ . 1 - $\dfrac{12}{19}$
= $\dfrac{7}{19}$ - $\dfrac{12}{19}$
= $\dfrac{-5}{19}$