12)

This is a triangle with angles $$120^\circ$$, $$30^\circ$$, and $$30^\circ$$. It is an isosceles triangle. The altitude to the base bisects the angle and the base. So we have two right-angled triangles with angles $$90^\circ$$, $$60^\circ$$, and $$30^\circ$$. The hypotenuse is $$16$$ cm. The side opposite $$30^\circ$$ is $$y$$. So $$y = 16/2 = 8$$ cm.