Let the speed of the train be x km/h.Distance covered by the train = 360 km

1st case- Time, T_{1}= distance / speed_{1} = 360 / x

2nd case- Time, T_{2}= distance / speed_{2} = 360 / x + 5

According to the question,

360 / x - 1 = 360 / x + 5(or) 360 / x - 360 / x + 5 = 1

360 (x+5) -360 (x) / x (x+5) =1

360x + 1800 - 360x / x^{2} + 5x = 1

1800 = x^{2} + 5x

x^{2} + 5x - 1800 =0

( Now u can do any of the methods i.e. factorisation or completing the square method or apply quadratic formula to find the speed.)

Hope You get it....! :)