You need to convert the 4 hr 7 min 29 s all to the same unit to start off with, the best thing to do usually is to convert to the smallest unit so we convert to seconds:
29s = 29s, no need to change anything there
7min = 7 X 60s = 420s
4h = 4 X 60min = 240min, 240 X 60s = 14,400s
Now that we've converted all the time units to the same unit (seconds), we add them together:
29 + 420 + 14,400 = 14,849s
Generally when we talk about speed and are using seconds as our unit for time, we express speed in m/s (metres per second), so now we convert the kilometres to metres:
1 km = 1000 m, so 42.2 km = 42.2 X 1000 = 42,200m
Finally, we can use our formula:
42,200 / 14,849 = 2.841942218 m/s
(I kind of rushed the calculations a little bit so that figure may not be 100% accurate, but the method is definitely correct)
Hope this helped :)
