TeX Quellcode:

\begin{array}{crcrcl} \text{II} & a+b &=& 6 &\vert& -b \cr \text{III} & 9a+3b &=& 30 \cr \cr \text{II} & a &=& 6-b \cr \text{III} & 9a+3b &=& 30 \cr \cr \text{II in III} & 9(6-b)+3b &=& 30 \cr & 54-9b+3b &=& 30 \cr & 54-6b &=& 30 &\vert& -54 \cr & -6b &=& -24 &\vert& :\left(-6\right) \cr & b &=& 4 \cr \cr \text{b in II} & a &=& 6-4 \cr & a &=& 2 \end{array}