Answer
$\pm\sqrt 3$
Work Step by Step
1. $2log_{13}(x+2)=log_{13}(4x+7) \Longrightarrow log_{13}(x+2)^2=log_{13}(4x+7) \Longrightarrow (x+2)^2=4x+7 \Longrightarrow x^2+4x+4=4x+7 \Longrightarrow x=\pm\sqrt 3$.
2. Check $x=\pm\sqrt 3$ fit(s).