$\frac{dq}{dt}=-4q+12$

$x^6-81\:$

$\frac{6}{m-4}=\frac{3}{m+2}$

$\tan\left(a\right)\cdot\cot\left(a\right)\cdot\sec\left(a\right)=\frac{1}{\cos\left(a\right)}$

$\frac{2x^3+x^3+3x^3}{x^2.x}$

$\left(abc-1\right)\left(2-abc+ab+bc\right)$

$\left(51\right)\left(2\right)$