Question 763519
Passenger train = x
Freight train = x - 12
348km/x-12 = 420/x
Cross multiply
348x = 420(x - 12)
348x = 420x - 5040
-72x = -5040
   -x = -70
    x = 70km/hr
Passenger train's speed = 70 km/hr
Freight train's speed = 58 km/hr
Proof:
348/58 = 420/70
    6 = 6
Hope this helps.
:-)