Ok, for clarity, let's try and break down these clues into formulas using the variable x:
If you multiply me by 2, I become a number greater than 20 and less than 40
40 > 2x >20
This can be simplified by dividing all three figures by 2, so we get:
20 > x > 10
This narrows x down to a number between 20 and 10...
If you multiple me by 6, I end in 8.
6x = _8
Let's try some of the possibilities out:
6 * 10 = 60
6 * 11 = 66
6 * 12 = 72
6 * 13 = 78 (we've got a possible winner...)
6 * 18 = 108 (and another)
So we now know it's either 13 or 18, let's test the next rule:
If you multiply me by 4, I end in 2.4 * 13 = 52
4 * 18 = 72
Uhoh! Bit of a problem, they both pass that test. And that's the end of the line unfortunately. The answer can be either 13 or 18.
