The figure below is formed by five straight lines, AC, AD, BD, BE and CE. Find the sum of $\angle p$, $\angle q$, $\angle r$ and $\angle s$. Ans : ___ $^\circ$

1. Identify the exterior angle of the triangle containing angles p and q

Let the intersection of $AD$ and $BE$ be $F$. In $\triangle BDF$, the exterior angle at $F$ is $\angle AFE = \angle p + \angle q$.

2. Identify the exterior angle of the triangle containing angles r and s

Let the intersection of $AC$ and $CE$ be $G$. In $\triangle CEG$, the exterior angle at $G$ is $\angle AGC = \angle r + \angle s$.

3. Use the sum of angles in a quadrilateral to find the sum of p, q, r, and s

Consider the quadrilateral formed by the intersections of $AC, AD, BE, CE$. Let the intersection of $AC$ and $BE$ be $H$, and the intersection of $AD$ and $CE$ be $I$. The interior angles of quadrilateral $FGHI$ are $\angle F = \angle p + \angle q$, $\angle G = \angle r + \angle s$, $\angle H = 60^\circ$ (vertically opposite), and $\angle I = 140^\circ$ (vertically opposite). The sum of interior angles of a quadrilateral is $360^\circ$.
$(\angle p + \angle q) + (\angle r + \angle s) + 60^\circ + 140^\circ = 360^\circ$
$\angle p + \angle q + \angle r + \angle s = 360^\circ - 200^\circ = 160^\circ$