Bạn tham khảo bên dưới:
${a)}$ $\frac{\frac{1}{9}-\frac{1}{7}-\frac{1}{11}}{\frac{4}{9}-\frac{4}{7}-\frac{4}{11}}$
${=}$ $\frac{\frac{1}{9}-\frac{1}{7}-\frac{1}{11}}{4.(\frac{1}{9}-\frac{1}{7}-\frac{1}{11})}$
${=}$ $\frac{1}{4}$
${b)}$ $\frac{51-\frac{6}{7}-\frac{3}{11}+\frac{3}{23}}{255-\frac{15}{11}+\frac{15}{23}-\frac{30}{7}}$
${=}$ $\frac{51-\frac{6}{7}-\frac{3}{11}+\frac{3}{23}}{5.(51-\frac{6}{7}-\frac{3}{11})}$
${=}$ $\frac{1}{5}$
