let the bridge be L miles long. Let Anoop run v miles per hour.
Hence by the time Anoop runs to EITHER END of the railroad bridge, the train just comes to the SAME end of the bridge.
1) Anoop runs L - 5L/6 = L/6 distance, to the nearer end of the bridge.
The train has to run through the distance x.
2) Anoop runs 5L/6 to the farther end of the bridge.
divide equation 2 by equation 1 =>
substitute in equation 1, Anoop can run at 23.66 mph