Atrain travels at a steady rate of 80 mph. if the train travels for one-half hour nonstop, what are the domain and range of the distance function during the trip?

The independent variable is time, which varies from 0 to 0.5, so domain = [0,0.5].
The distance travelled is the dependent variable, varying from 0 to (1/2)80=40 km.  The range is therefore [0,40].

Note: in interval notation, a square bracket means that the value is included in the interval.

49.6 is what i think it is.