Hello !
1/2 h ------> 120 / 2 = 60 km
1/4 h-------> 120 / 4 = 30 km
3/4 h ------> 120 / 4 * 3 = 90 km
1h30 ------> 120 * 1,5 = 180 km
210 km = 7 * 30 km ---------> 7 * 1/4 h = 1h45
570 km = 19 * 30 km ----------> 19 * 1/4 h = 4h45
15 km = 30 / 2 km-----------> 1/4 ÷ 2 = 1/8 = 7 mn 30 s