$a)$  

$\frac{3}{7}+\frac{5}{7}=\frac{8}{7}=1\frac{1}{7}$  

$\frac{6}{11}-\frac{4}{11}=\frac{2}{11}$  

$10-\frac{4}{5}=9\frac{5}{5}-\frac{4}{5}=9\frac{1}{5}$  

$7-3\frac{1}{6}=6\frac{6}{6}-3\frac{1}{6}=3\frac{5}{6}$  

 

$b)$    

$2\frac{3}{5}+7\frac{1}{5}=9\frac{4}{5}$  

$6\frac{3}{7}+8\frac{4}{7}=14\frac{7}{7}=15$  

$6\frac{8}{9}-2\frac{5}{9}=4\frac{3}{9}$  

$1\frac{2}{9}-\frac{7}{9}=\frac{11}{9}-\frac{7}{9}=\frac{4}{9}$  

 

$c)$    

$\frac{3}{4}+\frac{5}{8}=\frac{6}{8}+\frac{5}{8}=\frac{11}{8}=1\frac{3}{8}$  

$3\frac{1}{2}+4\frac{5}{6}=3\frac{3}{6}+4\frac{5}{6}=7\frac{8}{6}=8\frac{2}{6}$  

$\frac{2}{3}+\frac{3}{5}=\frac{10}{15}+\frac{9}{15}=\frac{19}{15}=1\frac{4}{15}$  

$\frac{2}{3}-\frac{3}{5}=\frac{10}{15}-\frac{9}{15}=\frac{1}{15}$  

 

$d)$  

$1\frac{2}{7}-\frac{1}{2}=\frac{9}{7}-\frac{1}{2}=\frac{18}{14}-\frac{7}{14}=\frac{4}{14}$

$2\frac{3}{4}-\frac{5}{12}=2\frac{9}{12}-\frac{5}{12}=2\frac{4}{12}$

$6\frac{1}{6}-3\frac{3}{8}=5\frac{7}{6}-3\frac{3}{8}=5\frac{28}{24}-3\frac{9}{24}=2\frac{21}{24}$

$9\frac{5}{8}-5\frac{7}{10}=9\frac{25}{40}-5\frac{28}{40}=8\frac{65}{40}-5\frac{28}{40}=3\frac{37}{40}$