Need help please :( I didn't understand how to do it)

Which of the following is most likely the next step in the series? a3z, b6y, c9x, d12w, е15v, f18u

What’s the answer ? use the picture to see the problem

In the diagram, points d and e are marked by drawing arcs of equal size centered at b such that the arcs intersect ba and bc. then, intersecting arcs of equal size are drawn centered at points d and e. point p is located at the intersection of these arcs. based on this construction, m , and m