Well I gave it a shot. My answer seems a litte out there because no human can run this fast but, I don't know where you got the problem from either.
Ta = the time for runner A to run 1km
Tb = the time for runner B to run 1km
Va = runner A's velocity
Vb = runner B's velocity
In the first senario Ta = Tb-(100m/Vb)-20s
In the second senario Ta = Tb-25s+(50m/Va)
Combining these two equations I got 5s-(100m/Vb) = 50m/Va
After solving that for Va = 50m/(5s-(100/Vb))
Plugging that back into this equation 1000m/Va = 900m/Vb-20s and solving for Vb you get Vb = 24.16m/s
After putting that back into the equation that relates Va and Vb I found that Va = 58.072m/s
Since Ta = 1000m/Va, the time it takes runner A to run one kilometer is about 17.25s which seems kind of ridiculous. I haven't done much math since I was in school about 5 years ago so I may be kind of rusty, but I checked it a couple of times and it seems to work out. I just hope I wrote the equations right. I hope this helps.
YES YOUR BOTH ANSWER IS CORRECT YOU ARE NICE IN MATH I HAVE A ANOUTHER QUESTION FOR YOU Question- in a race of one kilometre, A gives B a start of 100 metres and still wins by 20 seconds but if A gives B a start of 25 seconds B wins by 50 metres the time taken by A to run one kilometer is?
2 men = .4545*2=.9090
3 women = .3636*3=1.0908
4 kids = .1818*4=.7272
The 16 hectare field will be reaped in 8 days.
YOUR ANSWER IS RIGHT THANK YOU VERY MUCH