$\text{a)}\frac{4}{12}=\frac{2}{6}=\frac{1}{3}$  

$\text{b)}\frac{8}{16}\stackrel{\text{:2}}{=}\frac{4}{8}\stackrel{\text{:4}}{=}\frac{1}{2}$  

$\text{c)}\frac{12}{18}\stackrel{\text{:2}}{=}\frac{6}{9}\stackrel{\text{:3}}{=}\frac{2}{3}$    

$\text{d)}\frac{24}{64}\stackrel{\text{:2}}{=}\frac{12}{32}\stackrel{\text{:2}}{=}\frac{6}{16}\stackrel{\text{:2}}{=}\frac{3}{8}$  

$\text{e)}\frac{50}{200}\stackrel{\text{:10}}{=}\frac{5}{20}\stackrel{\text{:5}}{=}\frac{1}{4}$  

$\text{f)}\frac{42}{60}\stackrel{\text{:6}}{=}\frac{7}{10}$  

$\text{g)}\frac{45}{75}\stackrel{\text{:5}}{=}\frac{9}{15}\stackrel{\text{:3}}{=}\frac{3}{5}$  

$\text{h)}\frac{12}{60}\stackrel{\text{:2}}{=}\frac{6}{30}\stackrel{\text{:6}}{=}\frac{1}{5}$

$\text{i)}\frac{28}{70}\stackrel{\text{:7}}{=}\frac{4}{10}\stackrel{\text{:2}}{=}\frac{2}{5}$