Let $P(2,4,5)\:\:Q(3,5,-4)$ be the given two points.
From section formula. the point $R(x,y,z)$ that divides $PQ$ in the ratio $2:3$ externally is
given by $R(x,y,z)=\big(\large\frac{6-6}{2-3},\:\frac{10-12}{2-3},\:\frac{-8-15}{2-3}\big)$$=(0,-2,23)$
Since the $x\: coordinate$ of $R$ is $zero$, $R$ lies on $YOZ\:Plane.$