First you'll multiply 0.18 by any random number. In this case, I'll get 5:
0.18 * 5 = 0.9
Therefore 0.9 / 5 = 0.18 Even though this is a possible answer, there are many options. You only have to multiply 0.18 by the number you wish to work with.
Hope it helped,
BioTeacher101
