Equation of chord with given middle point $\begin{aligned}
& T=S_1 \
& \Rightarrow \frac{3 x}{25}+\frac{\mathrm{y}}{16}-1=\frac{9}{25}+\frac{1}{16}-1 \
& 48 \mathrm{x}+25 \mathrm{y}=144+25 \
& 48 \mathrm{x}+25 \mathrm{y}=169 \text { Ans. }
\end{aligned}$