\(\dfrac{7}{11}+\dfrac{9}{12}=\dfrac{16}{23}\Rightarrow\text{Sai, sửa}:\dfrac{7}{11}+\dfrac{9}{12}=\dfrac{61}{44}\)
\(\dfrac{5}{6}-\dfrac{4}{5}=\dfrac{1}{30}\Rightarrow\text{Đúng}\)
\(\dfrac{11}{12}+\dfrac{17}{18}=\dfrac{67}{36}\Rightarrow\text{Đúng}\)
\(\dfrac{13}{15}-\dfrac{13}{45}=\dfrac{2}{5}\Rightarrow\text{Sai, sửa}:\dfrac{13}{15}-\dfrac{13}{45}=\dfrac{26}{45}\)