I think this is the right section to post this but im not 100%

Find the time required for a train to reach 100m if Vo=20m/s (not sure how to do subext) and acceleration is $\displaystyle .5m/s^2$

$\displaystyle

s=20t+(1/2).5t^2

$

As far as i know, this is solved using the quadratic formula. How would i go about putting this equation into quadratic form so i can use the quadratic formula?