130=-15t^2+90t+10

Solution for 130=-15t^2+90t+10 equation:

130=-15t^2+90t+10

We move all terms to the left:

130-(-15t^2+90t+10)=0

We get rid of parentheses

15t^2-90t-10+130=0

We add all the numbers together, and all the variables

15t^2-90t+120=0

a = 15; b = -90; c = +120;
Δ = b2-4ac
Δ = -902-4·15·120
Δ = 900
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$t_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$t_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{900}=30$
$t_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-90)-30}{2*15}=\frac{60}{30}
=2
$
$t_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-90)+30}{2*15}=\frac{120}{30}
=4
$