Work out shortest path (dijkstra) instantly with clear inputs, formula shown and shareable results.
Dijkstra's algorithm settles vertices in order of increasing distance from the source, relaxing each outgoing edge as it goes. Non-negative weights guarantee that once a vertex is settled its distance is final.
Relaxation
if dist(u) + w(u,v) < dist(v) then dist(v) = dist(u) + w(u,v)
The route 1 → 3 → 5 → 4 → 6 costs 2 + 3 + 4 + 11 = 20, cheaper than going via vertex 2.
A negative edge could improve a distance already declared final. Bellman-Ford handles that case instead.