Step-by-step explanation:
[tex] \frac{ - 6a}{(3(1 - \frac{1}{2} a) - ( \frac{2}{3} - 3a) - a)a } = - 1 \\ \frac{ - 6a}{( \frac{3}{2} a + \frac{7}{3}a - a)a } = - 1 \\ \frac{6a}{ \frac{17}{6} a {}^{2} } = 1 \\ 6 = \frac{17}{6} a \\ a = \frac{(6 \times 6)}{17} \\ a = \frac{36}{17} [/tex]
