If you would like to know your final displacement, you can calculate this using the following steps:
x ... your house
at noon: 1.7 km north from x
at 6 pm: 5.4 km south
1.7 km - 5.4 km = 1.7 - 5.4 = -3.7 km
The correct result would be 3.7 km south from your house.