A train moving 66m long overtakes another train of 88m long,moving in the same direction in 0.168 min if the second train is moving at 30 km at what speed is the frist train moving

Answer 1

If you mean "overtaking" to include the full length of each train, then shifting to relative motion.
distance=relativevelocity*time changing distance to km, time to hr
(.066+.088)=(V-30km/hr )*(.168/60 hr)
.154/.0028= V-30km/hr
solve for V in km/hr. Fast train.