źródło:
\frac{\frac{3}{4}-\frac{2}{3}}{\frac{2}{3}-\frac{1}{2}}=
=\frac{\frac{9}{12}-\frac{8}{12}}{\frac{4}{6}-\frac{3}{6}}=\frac{\frac{1}{12}}{\frac{1}{6}}=\frac{1}{12}:\frac{1}{6}=\frac{1*6}{12*1}=\frac{1}{2}