Answer:
20. Tabitha's error is that instead of solving the equation she just wrote down the mixed fraction as if it was a decimal. In order to get the correct answer she needed to do:
2 1/6
2*6 = 12
12 + 1 = 13
Improper fraction = 13/6
13/6 = 2.17
The correct answer would be 2.17 miles