Question:
The sum of the interior angles of a polygon is three times the sum of its exterior angles. Determine the number of sided of the polygon.
Solution:
$\left\{(2 \mathrm{n}-4) \times 90^{\circ}\right\}=3 \times\left(\frac{360^{\circ}}{\mathrm{n}} \times \mathrm{n}\right)$
$\Rightarrow(\mathrm{n}-2) \times 180=3 \times 360$
$\Rightarrow \mathrm{n}-2=6
$\therefore \mathrm{n}=8$