Answer:
24 miles.
Step-by-step explanation:
Jackie traveled four times as many miles by bus as by foot. This means that the number of miles travelled by bus is 4 units, and the number of miles travelled by foot is 1 unit.
Jackie traveled three times as many miles by train as by bus. We know that the number of miles travelled by bus is 4 units, so the number of miles travelled by train is
units.
Total number of units: 

Divide 17:

The number of miles travelled by train is 12 units:

She travelled 24 miles by train.