.
One line solution (as it should be)
The diesel train speed = = 42 miles per hour.
-------------
All such problems and each such problem can be solved in one line and should be solved in one line - if you know how to do it.
To learn on how to solve such problems in one line, you need practice.
See the lessons
- Travel and Distance problems
- Travel and Distance problems for two bodies moving in opposite directions
- Travel and Distance problems for two bodies moving in the same direction (catching up)
in this site. They were written specially for you to give you practice.
You will find the solutions of many similar problems there.
Read them and learn once for all from these lessons on how to solve simple Travel and Distance problems.
Become an expert in this area.
=============
Did I say "in one line ?" - No. In a quarter of line.