Question 971845
I need a bit more information, but what appears to me important is the lack of units.

If she misses the train, the time t needs 7 more MINUTES.

Later on, t =41, that is minutes.
d=rt, and rate (if she is walking, is 3 miles PER HOUR), which is a walking speed.

Given that alone, she walked just over 2 miles, since 3 miles per hour *40 minutes (2/3) hour, is 2 miles.