[jay_shark]

The total distance that Jim walks divided by the total distance that Mike walks should be in the ratio 2:2.5 .

So Jim walked a total distance of 2/(2+ 2.5)*20 = (2/4.5)*20

Speed = Distance/Time .
2=[2/4.5*20]/T

Solve for T and we get T= 20/4.5 s

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Solution 2 :

Total distance traveled by Jim and Mike is 20m .

Distance jim travels as a function of time(s) is 2t
Distance Mike travels as a function of time(s) is 2.5t

So 2t + 2.5t = 20
Solve for t and we get 4.5t=20 and t =20/4.5s

Now we use that Speed = distance/time
2=distance/{20/4.5)

Solve for distance and we get distance = 2/4.5*20