Answer:
[tex]:\implies \sf -6x + 3x = -21 \\ \\ \\ [/tex]
[tex]:\implies \sf - 3x = -21\\ \\ \\ [/tex]
[tex]:\implies \sf x = \dfrac{-21}{ - 3} \\ \\ \\ [/tex]
[tex]:\implies \sf x = \dfrac{21}{3} \\ \\ \\ [/tex]
[tex]:\implies \underline{ \boxed{ \textsf { \textbf{x = 7}}}} \\ [/tex]
