First, express the problem as an equation. 'Seven more' means +7, 'twice John's age' means 2J. Let's express it.
[tex]7+2J=55[/tex]Once we express the equation, solve for J.
First, subtract 7 from each side.
[tex]\begin{gathered} 7-7+2J=55-7 \\ 2J=48 \end{gathered}[/tex]Second, divide each side by 2.
[tex]\begin{gathered} \frac{2J}{2}=\frac{48}{2} \\ J=24 \end{gathered}[/tex]