30=-5t^2+5t+60

Solution for 30=-5t^2+5t+60 equation:

30=-5t^2+5t+60

We move all terms to the left:

30-(-5t^2+5t+60)=0

We get rid of parentheses

5t^2-5t-60+30=0

We add all the numbers together, and all the variables

5t^2-5t-30=0

a = 5; b = -5; c = -30;
Δ = b2-4ac
Δ = -52-4·5·(-30)
Δ = 625
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$t_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$t_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{625}=25$
$t_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-5)-25}{2*5}=\frac{-20}{10}
=-2
$
$t_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-5)+25}{2*5}=\frac{30}{10}
=3
$