$\forall$$p$:FinProbSpace, $n$:$\mathbb{N}$, $X$, $Y$, $Z$:RandomVariable($p$;$n$).
\\[0ex]rv{-}disjoint($p$;$n$;$X$;$Y$) $\Rightarrow$ rv{-}disjoint($p$;$n$;$X$;$Z$) $\Rightarrow$ rv{-}disjoint($p$;$n$;$X$;$Y$ + $Z$)