$8\frac{2}{5}= 8+\frac{2}{5}=\frac{8\times 5+2}{5}=\frac{42}{5}$

$5\frac{3}{4}= 5+\frac{3}{4}=\frac{5\times 4+3}{4}=\frac{23}{4}$

$4\frac{3}{7}= 4+\frac{3}{7}=\frac{4\times 7+3}{7}=\frac{31}{7}$

$2\frac{1}{10}= 2+\frac{1}{10}=\frac{2\times 10+1}{10}=\frac{21}{10}$