If you don't answer this in the next 5 seconds, tomorrow morning you will step on a LEGO trying to grab the milk from the fridge.

Answer:
d = 78 [km]
Explanation:
The displacement shift was from Tipton to Iowa city, so we have:
d1 = 27[km]
Then he travels back for 15[km]
d2 = 15[km]
Finally he returns back to Iowa city the displacement 36 [km]
d3 = 36[km]
d = d1 + d2 + d3
d = 27 + 15 + 36
d = 78 [km]