TITLE: How do you call the relation between these 2 variables?
QUESTION [6 upvotes]: Let's say I have an X number and I want to increment it by 50%, I would get 
$X*A=Y$
Then in order to multiply Y and get X again I would need to do
$Y*Z=X$
How do you call the relation between A and Z?
Example with numbers:
$$5*1.5=7.5$$
$$7.5*Z=5$$
$$Z=0.66$$
How do you call the relation between 1.5 and 0.66 when $X*1.5*0.66=X$?

REPLY [10 votes]: A and Z are multiplicative inverses; i.e., A × Z = 1.
Therefore, X × A × Z = X
Usually, we just say that A is the inverse of Z (and vice-versa).