Two trains start simultaneously from opposite ends of a 180-km route and travel toward each other on parallel tracks. Train X, traveling at a constant rate, completes the 180-km trip in 5 hours. Train Y, travelling at a constant rate, completes the 180-km trip in 4 hours. How many kilometers had Train X traveled when it met Train Y? Choose the most appropriate option
A) 72 B) 74 C) 76 D) 78 E) 80
If the two trains cover a total distance D, then Train X travels (4/9)*D while Train Y travels (5/9)*D. If the trains travel 180 km to the meeting point, then Train X travels  (4/9)*180= 
<gadget id="calculator"> (4/9)*180</gadget>
<output>80</output>
80 km. The answer is 80.
<result>E</result>
Two trains start simultaneously from opposite ends of a 180-km route and travel toward each other on parallel tracks. Train X, traveling at a constant rate, completes the 180-km trip in 5 hours. Train Y, travelling at a constant rate, completes the 180-km trip in 4 hours. How many kilometers had Train X traveled when it met Train Y?