2 problems

Let $K_n$ be the complete graph on $n$ vertices, and let a good drawing of $K_n$ be a drawing in which edges meet only at common endpoints or proper crossings, with no three edges…

Let $D(K_n)$ be a good drawing of the complete graph $K_n$ with vertex set of size $n$. An empty triangle is a triangular face of the drawing whose boundary consists of three edges…