0.2*t^2-3t+10.4=100

Solution for 0.2*t^2-3t+10.4=100 equation:

0.2t^2-3t+10.4=100

We move all terms to the left:

0.2t^2-3t+10.4-(100)=0

We add all the numbers together, and all the variables

0.2t^2-3t-89.6=0

a = 0.2; b = -3; c = -89.6;
Δ = b2-4ac
Δ = -32-4·0.2·(-89.6)
Δ = 80.68
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$t_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$t_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$t_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-3)-\sqrt{80.68}}{2*0.2}=\frac{3-\sqrt{80.68}}{0.4}
$
$t_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-3)+\sqrt{80.68}}{2*0.2}=\frac{3+\sqrt{80.68}}{0.4}
$