Associated Prime notation

Question

Let $I$ be an ideal of ring $R$ with $I\neq R$. Prime ideal $P$ of $R$ is said to be an associated prime of $I$ in the sense of Bourbaki, if $P=(I :_R x)$ for some $x\in R$. In this case we say that $P$ is a $ B$-prime of $I$.

Can anyone explain meaning of notation $(I :_R x)$?

Answer 1

Presumably it is $(I:_Rx):=\{r\in R:rx\in I\}$. Typically we suppress the subscript $R$.