Let: v = Olga's speed t = the time Anna spent going to school (3 km/hour) t/2 = the time Anna spent running back home with speed of 6 km/hour So, t + t/2 = 3t/2 is the total time In the meantime distance = speed*time and the both made the same distance we can put it as: 3t + 6*(t/2) = (3t/2)*v 6t = (3/2)tv divide both sides by t (3/2)v = 6 v = 2*6/3 v = 4 km/hour Olga's speed was 4 km/hour.