Question 1095743
<br>In the time that Mike runs the full 28km, Nathan runs 24km, and Oliver runs 18km.  Comparing those distances for Nathan and Oliver, we can see that Oliver runs 3/4 as fast as Nathan (18/24 = 3/4).<br>
When Nathan finishes the full 28km, Oliver will have run 3/4 of 28km, or 21km; so he still has 7km to run when Nathan finishes.