$a)\frac{4}{7}+\frac{2}{7}=\frac{6}{7}$

$\frac{3}{10}+\frac{3}{10}=\frac{6}{10}=\frac{3}{5}$

$\frac{4}{15}+\frac{2}{15}=\frac{6}{15}=\frac{2}{5}$

$\frac{5}{9}+\frac{3}{9}=\frac{8}{9}$

$\frac{1}{9}+\frac{2}{9}=\frac{3}{9}=\frac{1}{3}$

$\frac{1}{4}+\frac{1}{4}=\frac{2}{4}=\frac{1}{2}$

  $\frac{2}{10}+\frac{5}{10}=\frac{7}{10}$  

$\frac{1}{10}+\frac{7}{10}=\frac{8}{10}=\frac{4}{5}$

$\frac{1}{6}+\frac{2}{6}=\frac{3}{6}=\frac{1}{2}$

 

 

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

$\frac{3}{5}+\frac{2}{5}=\frac{5}{5}=1$

$\frac{5}{9}+\frac{8}{9}=\frac{13}{9}=1\frac{4}{9}$

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

$\frac{7}{10}+\frac{5}{10}=\frac{12}{10}=\frac{6}{5}=1\frac{1}{5}$

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