The given phrases are interpreted as:
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X = number. 4X + 9 = 2X - 15 ===========
The mystery number is less than one (a fractional number).
No, however there are even numbers less than 15. An even number is any number that can be divided by two evenly, so it can be greater than 15 too.
15/17 is less than 1. 17/15 is more than 1.
25