(i) $\quad \mathrm{A}(9,3)$ and $\mathrm{B}(15,11)$

The given points are $A(9,3)$ and $B(15,11)$.

Then $\left(x_{1}=9, y_{1}=3\right)$ and $\left(x_{2}=15, y_{2}=11\right)$

$A B=\sqrt{\left(x_{2}-x_{1}\right)^{2}+\left(y_{2}-y_{1}\right)^{2}}$

$=\sqrt{(15-9)^{2}+(11-3)^{2}}$

$=\sqrt{(15-9)^{2}+(11-3)^{2}}$

$=\sqrt{(6)^{2}+(8)^{2}}$

$=\sqrt{36+64}$

$=\sqrt{100}$

$=10$ units

(ii) $\quad \mathrm{A}(7,-4)$ and $\mathrm{B}(-5,1)$

The given points are $\mathrm{A}(7,-4)$ and $\mathrm{B}(-5,1)$.

Then, $\left(x_{1}=7, y_{1}=-4\right)$ and $\left(x_{2}=-5, y_{2}=1\right)$

$\mathrm{AB}=\sqrt{\left(\mathrm{x}_{2}-\mathrm{x}_{1}\right)^{2}+\left(\mathrm{y}_{2}-\mathrm{y}_{1}\right)^{2}}$

$=\sqrt{(-5-7)^{2}+\{1-(-4)\}^{2}}$

$=\sqrt{(-5-7)^{2}+(1+4)^{2}}$

$=\sqrt{(-12)^{2}+(5)^{2}}$

$=\sqrt{144+25}$

$=\sqrt{169}$ $=13$ units

$=\sqrt{144+25}$

$=\sqrt{169}$

$=13$ units