Least Common Denominator

 $\frac{6}{7\ }\ -\ \frac{1}{2}$  

 $\frac{1}{6}\ +\ \frac{2}{5}$  

 $\frac{5}{9}\ -\ \frac{1}{3}$  

 $\frac{1}{8}\ +\ \frac{3}{4}$  

 $\frac{5}{7}\ -\ \frac{2}{3}$  

 $\frac{2}{5}\ +\ \frac{1}{4}$  

 $\frac{5}{6}\ -\ \frac{3}{4}$  

 $\frac{3}{4}\ -\ \frac{3}{7}$