Answer :
[tex]7x-42=7(x-6)[/tex]
Let's check every expression:
[tex]\begin{gathered} 7(x-42)\ne7(x-6) \\ \end{gathered}[/tex]This expression is not equivalent.
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[tex]7(x-6)=7(x-6)[/tex]This expression is equivalent
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[tex](4+3)x-42=(7)x-42=7x-42[/tex]This expression is equivalent
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[tex]\begin{gathered} 8(x-42)-(x-42) \\ 8x-336-x+42=7x-294\ne7x-42 \end{gathered}[/tex]This expression is not equivalent