The simplest triangle is shown in figure is 12 and another is IBO, BDO, DGO, GIO, ABO,CBD, DEO, IBD,BDG, DGI, GIB, ACO and COE and ACE is the total no of traingle are 12+14=26
Since Nithya and Suganya exchange places, so Rita’s new position is the same as Monika’s earlier position. This position is 17th from the right and 10th from the left. Therefore Number of girls in the row = (16 + 1 + 9) = 26.