\[y = 4x - 20;\ \ y = 5x - 30\]
\[4x - 20 = 5x - 30\]
\[5x - 4x = - 20 + 30\]
\[x = 10.\]
\[y = 4 \bullet 10 - 20 = 40 - 20 = 20.\]
\[Ответ:(10;20).\]