Answer:
No*
Explanation:
The sum of the two distances is 8.36+13.85 = 22.21 km. Most folks probably would not agree that this is "about 30." 20 km, or even 25 km, might be better estimates of Tracy's distance from the school.
Tracy has significantly overstated the distance she lives from the school.
___
* It depends on the context. The distance estimate of itself may not be what is of interest. In the context of estimating required fuel for the trip, for example, one might want to over-estimate rather than underestimate the distance. The same might be true for estimating the required travel time.