3. Given an angle of $13^{0}$. How to obtain an angle of $11^{0}$?
3. One possible option: lay off the angle of $13^{0}$, 13 times, then the difference between the straight angle and the obtained angle will give the required angle $\left(180^{\circ}-13 \cdot 13^{0}=11^{\circ}\right)$