TeX Quellcode:

\begin{array}{rcl} 3\cdot\dfrac{15}{13} &=& \dfrac{15}{4+\frac{15}{13}} \cr\cr\dfrac{45}{13} &=& \dfrac{15}{\frac{67}{13}} \cr\cr\dfrac{45}{13} &=& \dfrac{195}{67} \end{array}