Complex sentence: A full-length train of six cars consists of two identification numbers, one for the first three cars, and the other the same number plus 1 for the other three, where the smaller number is always an odd number.
Split into simpler sentences: A full-length train of six cars consists of two identification numbers, one for the first three cars, and another for the second three. The bigger number is always equal to the smaller number plus one, and the smaller number is always an odd number.