Answer:
Step-by-step explanation:
The ratio of the two numbers is 18/27 = (2·9)/(3·9) = 2/3.
So, if you're starting with 27 and you want to scale it down to 18, you multiply by the scale factor 2/3.
If you're starting with 18 and you want to scale it up to 27, you use the inverse of the above scale factor. That inverse is 3/2.