This is a long question whilch i think involves the quadratic formula, but i generally dont know where to start with this so any help would be much appreciated.

"In an engineering test, a rocket sled is propelled into a target. The sled’s distancedin meters from the target is given by the formula d = -1.5t^2 + 120 wheretis the number of seconds after rocket ignition. How many seconds have passed since rocket ignition when the sled is 10 meters from the target?"