The relationship between speed, distance, and time is easily remembered when you consider that speed is written in terms of units of distance per units of time. (miles per hour, or kilometers per hour, for example) Of course "per" means "divided by".
speed = distance/time
speed = (750 m)/(1/3 h) = 2250 m/h = 2.25 km/h
Logan's average speed is 2.25 kilometers per hour.