216=6t^2+30t

Solution for 216=6t^2+30t equation:

216=6t^2+30t

We move all terms to the left:

216-(6t^2+30t)=0

We get rid of parentheses

-6t^2-30t+216=0

a = -6; b = -30; c = +216;
Δ = b2-4ac
Δ = -302-4·(-6)·216
Δ = 6084
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$t_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$t_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{6084}=78$
$t_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-30)-78}{2*-6}=\frac{-48}{-12}
=+4
$
$t_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-30)+78}{2*-6}=\frac{108}{-12}
=-9
$