$\frac{16}{80}$ =$\frac{16\div 8}{80\div 8}$ = $\frac{2}{10}$
$\frac{64}{800}$ = $\frac{64\div 8}{800\div 8}$ = $\frac{8}{100}$
$\frac{9}{25}$ = $\frac{9\times 4}{25\times 4}$ = $\frac{36}{100}$
$\frac{12}{250}$ = $\frac{12\times 4}{250\times 4}$ = $\frac{48}{1000}$