I suspect both the speed and retardation are given with incorrect units. I assume the latter is 6 m/s^2.

Before application of brakes, the vehicle travels

(54 km/s)(0.2 s) = 10.8 km

After application of brakes, the vehicle travels

(54 km/s)^2/(2*6 m/s^2)

= 54^2/.012 km

= 243000 km

The vehicle takes a total of 243,010.8 km to stop.

Before application of brakes, the vehicle travels

(54 km/s)(0.2 s) = 10.8 km

After application of brakes, the vehicle travels

(54 km/s)^2/(2*6 m/s^2)

= 54^2/.012 km

= 243000 km

The vehicle takes a total of 243,010.8 km to stop.