\[\frac{60a^{2} - b}{10a} - 6a^{\backslash 10a} = \frac{60a^{2} - b - 60a^{2}}{10a} =\]
\[= - \frac{b}{10a}\ \]
\[при\ a = 1,2;b = - 18:\]
\[- \frac{b}{10a} = \frac{18}{10 \cdot 1,2} = \frac{18}{12} = \frac{3}{2} = 1,5.\]