Let x=train speed

Let y = car speed

speed = distance / time

time = distance / speed

6 hours 30 minutes = 6.5 hours <== 400 km by train ; 200 km by car

1/2 hour longer = 7 hours <== 200 km by train ; 400 km by car

Train time + car time = total time

400 / x + 200 / y = 6.5 <== two equations and two unknowns

200 / x + 400 / y = 7 . . . . . . solve for x and y

400y + 200x = 6.5 xy

200y + 400x = 7 xy

400y - 6.5 xy = - 200x

200y - 7xy = - 400x

y ( 400 - 6.5x) = -200x

y ( 200 - 7x) = -400x

y (6.5x - 400) = 200x

y (7x - 200) = 400x

y = 200x / (6.5x - 400)

y = 400x / (7x - 200) . . . note this equation ... for later use

. . . since both equal y, the difference is zero

200x / (6.5x - 400) - 400x / (7x - 200) = 0

200x ( 7x - 200) - 400x (6.5x - 400) = 0

1400x^2 - 40000x - 2600x^2 + 160000x = 0

120000 x - 1200 x^2 = 0

100 - x = 0

x = 100 km / h <===== train speed

y = 400x / (7x - 200) . . . see note above

y = 400 * 100 / (7 * 100 - 200)

y = 80 km / h <===== car speed

hope i helped u:)