Answer:
-1/6 unit and 7/6 unit are both 2/3 unit from 1/2 unit.
Explanation:
1/2 unit is the "center." We first add 2/3 unit to 1/2 unit, obtaining 7/6 unit, and then subtract 2/3 unit from 1/2 unit, obtaining -1/6 unit. Both of these results are a distance of 2/3 unit from 1/2 unit.