This problem has more holes than swiss cheese.
ASSUME that the time he drives only depends on the distance he covers,
and has nothing to do with his speed or how he drives.
The race rules say he has to cover at least 50 km,
so the minimum time he can drive is the solution to
[ 50 = 3t + 47 ]
Subtract 47 from each side:
3 = 3t
Divide each side by 3 :
1 = t minimum
He has fuel for exactly 53 km, so the maximum time
he can drive is the solution to
[ 53 = 3t + 47 ]
Subtract 47 from each side :
6 = 3t
Divide each side by 3 :
2 = t maximum
