Just came across a question on my homework assignment. The only thing it says is:
What is $\leq ^{-1}$?
It is on chapter for relations.
I'm guessing it means:
$R \leq R^{-1}$, for $R$ being a relations, then having $R$ factored out on each sides??
If it helps, the book I'm using is Mathematics: A Discrete Introduction, Chapter 14, exercise 14.12
Given a relation $R$, the relation $R^{-1}$ is another relation:$$a\mathrel{R^{-1}}b\iff b\mathrel Ra.$$