$a)\frac{1}{5}+1\frac{4}{5}=1\frac{5}{5}=2$  

$b)2\frac{3}{5}-1\frac{2}{5}=1\frac{1}{5}$  

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

$d)2\frac{5}{9}+\frac{8}{9}=2\frac{13}{9}=3\frac{4}{9}$  

$e)3\frac{5}{7}+5\frac{6}{7}=8\frac{11}{7}=9\frac{4}{7}$  

$f)8\frac{1}{4}-6\frac{3}{4}=7\frac{5}{4}-6\frac{3}{4}=1\frac{2}{4}=1\frac{1}{2}$