\[12a^{2} - 12ax - 7a + 7x =\]
\[= 12a(a - x) - 7 \bullet (a - x) =\]
\[= (a - x)(12a - 7),\]
\[при\ a = 1\frac{1}{6} = \frac{7}{6};\ x = \frac{2}{3}:\]
\[\left( \frac{7}{6} - \frac{2}{3} \right)\left( 12 \bullet \frac{7}{6} - 7 \right) =\]
\[= \left( \frac{7 - 2 \cdot 2}{6} \right)\left( \frac{2 \cdot 7}{1} - 7 \right) =\]
\[= \frac{3}{6} \cdot (14 - 7) = \frac{1}{2} \cdot 7 = 3,5.\]