[tex] \left \{ {{-x+9 \geq 0} \atop {-x=9\ \textless \ 3}} \right.
\left \{ {{x \leq 9} \atop {-x+9\ \textless \ 3}} \right.
\left \{ {{x \leq 9} \atop {x-x\ \textless \ -6}} \right.
\left \{ {{x \leq 9} \atop {x\ \textgreater \ 6}} \right.
RS: x ∈<6,9]