This reduces to a simple addition problem.
You walk 1/6 or one sixth of a mile, then 1/3 or one third of a mile.
The result is 1/3 + 1/6.
Using basic properties of fractions, we can substitute 2/6 for 1/3:
2/6 + 1/6 = 3/6.
3/6 is three sixths, which is exactly 1/2.
So in total, you walked 1/2 miles.
