What Is John's Resultant Displacement on the Highway?

[rdhddstpchld9]

While John is traveling along a straight inter-
state highway, he notices that the mile marker
reads 236 km. John travels until he reaches
the 140 km marker and then retraces his path
to the 173 km marker.
What is John’s resultant displacement from
the 236 km marker?
Answer in units of km.

I keep getting 63, but the computer says it's wrong

 

[alex3]

Displacement is a vector, it has direction as well as magnitude.