Let $P = (\Omega, \mathcal{F}, \mathbb{P})$ be a D1159: Probability space such that

(i)	$X : \Omega \to \mathbb{R}$ is a D3161: Random real number on $P$

Let $B \subseteq \mathbb{R}$ be a D5113: Standard real Borel set.

Then \begin{equation} \{ X \in - B \} = \{ - X \in B \} \end{equation}

Let $P = (\Omega, \mathcal{F}, \mathbb{P})$ be a D1159: Probability space such that

(i)	$X : \Omega \to \mathbb{R}$ is a D3161: Random real number on $P$

Let $B \subseteq \mathbb{R}$ be a D5113: Standard real Borel set.

Then \begin{equation} \{ \omega \in \Omega : X(\omega) \in - B \} = \{ \omega \in \Omega : - X(\omega) \in B \} \end{equation}