[m]\frac{11}{14}-\frac{1}{6}=\frac{33}{42}-\frac{7}{42}=\frac{33-7}{42}=\frac{26}{42}=\frac{13}{21}[/m]
[m]\frac{7}{39}\cdot \frac{13}{21}=\frac{7\cdot 13}{39\cdot 21}=\frac{1}{9}[/m]
2.
[m]\frac{24}{49} : \frac{6}{7}=\frac{24}{49}\cdot \frac{7}{6}=\frac{24\cdot 7}{49\cdot 6}=\frac{4}{7}[/m]
[m]\frac{4}{7}+\frac{1}{14}=\frac{8}{14}+\frac{1}{14}=\frac{9}{14}[/m]