Atrain leaves kaduna for lagos at 64km/h and an express to kaduna leaves lagos an hour later at 96km/h. if the distance between kaduna and lagos is 624km, how far are the trains from lagos when they meet

Good to see you here. Now back to the train. 

Kaduna, K                                                                                   Lagos, L
 
Train leaves at 64 km/h

One hour late second train leaves Lagos at 96 km/h.

At the point they meet, if first train has been travelling for "x" hours. Second train has been travelling for (x-1) hour.

At the point the meet, the total distance travelled is equal to 624 km.

Therefore:

64(x) + 96(x-1) = 624
64x + 96x - 96 = 624
160x = 624+96
160x =       720             , x = 720/160 = 4.5

So when they meet, the first train which left Kaduna has travelled= 64x = 64*4.5= 288km from Kaduna.

So it is (624-288) km from Lagos. = 336 Km from Lagos.

Second train which left Lagos has travelled = 96(x-1) = 96(4.5-1) = 336km.
The second train is also 336 km away from Lagos.

Cheers.

Logical equivalent of the give question is its contrapositive