Answer :
If y varies directly with x means that there is going to be a constant of proportionality between them in the form
[tex]y=kx[/tex]use the data of y=6 when x=18 to find the constant of proportionality
[tex]\begin{gathered} 6=k\cdot18 \\ k=\frac{6}{18} \\ k=\frac{1}{3} \end{gathered}[/tex]use k to find the value of y when x=12
[tex]\begin{gathered} y=\frac{1}{3}(12) \\ y=4 \end{gathered}[/tex]