Answer :
[tex]\begin{gathered} 9x-7=-7 \\ \text{Step 1: Add 7 to both sides:} \\ 9x-7+7=-7+7 \\ 9x=0 \\ \text{step 2: Divide both sides by 9} \\ \frac{9x}{9}=\frac{0}{9} \\ x=0 \\ \end{gathered}[/tex]
The mistake is the step 2. You need to divide both sides by 9, not multiply both sides by 9