Let the number of stations after the increase be A, the number of stations before the increase be B, and a(a- 1)-b(b- 1)=26, and deduce a+b= 14 and a-b=2, and get A = 8.

You got it? In fact, this problem is not well thought out. If you consider another question, it will be another answer. For example, the return flight of the air ticket is different. For example, Shijiazhuang-Beijing, Beijing-Shijiazhuang, if this is calculated, it should be 6 platforms plus 2, then 8, 26 kinds of tickets.