Let's begin by listing out the information given to us:
[tex]\begin{gathered} f\mleft(x\mright)=3x \\ g\mleft(x\mright)=x-2 \end{gathered}[/tex]We will caculate fºg thus:
[tex]\begin{gathered} fºg=f(g(x))=3(x-2)=\text{3x}-6 \\ fºg=3x-6=0\Rightarrow3x=6\Rightarrow\frac{3x}{3}=\frac{6}{3}\Rightarrow x=2 \\ x=2 \end{gathered}[/tex]Hence, option B is correct
