Answer:
365.0 mi/h; 356.5 mi/h
Explanation:
Let x = speed of first train
and y = speed of second train
We have two conditions:
(1) x + y = 721.5
(2) x = y + 8.5
Subtract y from each side of (2) (3) x - y = 8.5
Add (1) and (3) 2x = 730.0
Divide each side by 2 (4) x = 365.0
Substitute (4) into (1) 365.0 + y = 721.5
Subtract 365.0 from each side y = 356.5
The first train travels at 365.0 mi/h, and the second train travels
at 356.5 mi/h.
Check:
365.0 + 356.5 = 721.5 365.0 = 356.5 + 8.5
721.5 = 721.5 365.0 = 365.0