TeX джерело:

\left\{ \begin{array}{l}2\lg x = 12,\\ - 2\lg y = 2;\end{array} \right.\;\left\{ \begin{array}{l}\lg x = 6,\\\lg y = - 1;\end{array} \right.\;\left\{ \begin{array}{l}x = {10^6},\\y = {10^{ - 1}}.\end{array} \right.