Let the line $A B$ makes intercepts a and $\mathrm{b}$ on the axes. The point $R(h, k)$ divides it in the ratio $1: 2$


$\begin{array}{ll}
\therefore & h=\frac{1 \times 0+2 \times a}{1+2}=\frac{2 a}{3} \\
\therefore & a=\frac{3}{2} h \text { and } k=\frac{1 \times b+2 \times 0}{1+2}=\frac{b}{3}
\end{array}$
$\therefore \quad b=3 k$
Intercept form of the line $A B$ is
$\begin{gathered}
\frac{x}{a}+\frac{y}{b}=1 \Rightarrow \frac{x}{\frac{3 h}{2}}+\frac{y}{3 k}=1 \\
\Rightarrow \quad \frac{2 x}{3 h}+\frac{y}{3 k}=1 \Rightarrow 2 k x+h y=3 k h
\end{gathered}$