30=6+70t-16t2

Solution for 30=6+70t-16t2 equation:

30=6+70t-16t^2

We move all terms to the left:

30-(6+70t-16t^2)=0

We get rid of parentheses

16t^2-70t-6+30=0

We add all the numbers together, and all the variables

16t^2-70t+24=0

a = 16; b = -70; c = +24;
Δ = b2-4ac
Δ = -702-4·16·24
Δ = 3364
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$t_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$t_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{3364}=58$
$t_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-70)-58}{2*16}=\frac{12}{32}
=3/8
$
$t_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-70)+58}{2*16}=\frac{128}{32}
=4
$