We need to solve the following equation:
[tex]\begin{gathered} 2(3+x)=18 \\ \end{gathered}[/tex]In order to do that, we have to isolate the "x" variable on the left side.
[tex]\begin{gathered} 2\cdot3+2\cdot x=18 \\ 6+2\cdot x=18 \\ 2\cdot x=18-6 \\ 2\cdot x=12 \\ x=\frac{12}{2} \\ x=6 \end{gathered}[/tex]The value of x is 6.
