$\text{a)}1\frac{2}{5}+1\frac{1}{5}=2\frac{3}{5}$

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

 

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

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

 

$\text{c)}3\frac{1}{3}+\frac{2}{3}=3\frac{3}{3}=4$

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