\[ \frac{3(3x-1)}{12} - \frac{4(20-x)}{12} = 5 \]
\[ \frac{9x - 3 - (80 - 4x)}{12} = 5 \]
\[ \frac{9x - 3 - 80 + 4x}{12} = 5 \]
\[ \frac{13x - 83}{12} = 5 \]
\[ 13x - 83 = 5 \times 12 \]
\[ 13x - 83 = 60 \]
\[ 13x = 60 + 83 \]
\[ 13x = 143 \]
\[ x = \frac{143}{13} \]
\[ x = 11 \]
Ответ: 11