Question 766801
Liza runs at 2m/sec 
Tanya runs at 3m/sec
3600 seconds in one hour
So Liza ran 2 * 3600 = 7200m
and Tanya ran 3 * 3600 = 10800m
Total = 18000m = 18km
So they are 18km apart after an hour.
Hope this helps.
:-)