Помогите 7,8. Пожалуйста!!!

$\frac{6a}{7c}$ - $\frac{36a²+49c²}{42ac}$ + $\frac{7c-36a}{6a}$ = $\frac{252a²c-252a²c+343c³}{294ac²}$ + $\frac{7c-36a}{6a}$ = $\frac{343c³}{294ac²}$ + $\frac{7c-36a}{6a}$ = $\frac{343c}{294a}$ + $\frac{7c-36a}{6a}$ = $\frac{7c}{6a}$ + $\frac{7c-36a}{6a}$ = $\frac{7c + 7c-36a}{6a}$ = $\frac{14c-36a}{6a}$ = $\frac{14*69-36*77}{6*77}$ = $\frac{14*69-36*77}{6*77}$ = $\frac{966-2772}{462}$ = $\frac{966-2772}{462}$ = $\frac{-1806}{462}$ = - $\frac{903}{231}$ = - $\frac{129}{33}$ = - $\frac{43}{11}$

8) 1