$\frac{5}{7}$ . $\frac{5}{11}$ + $\frac{5}{7}$ . $\frac{2}{11}$ - $\frac{5}{7}$ . $\frac{4}{11}$
= $\frac{5}{7}$ . ($\frac{5}{11}$ + $\frac{2}{11}$ - $\frac{4}{11}$)
= $\frac{5}{7}$ . $\frac{5 + 2 - 4}{11}$
= $\frac{5}{7}$ . $\frac{3}{11}$
= $\frac{15}{77}$
Chúc học tốt!!!