I would like some help on this.

Any applicent that went for 3-5, 6-8, or 9-11 went to fewer than 12 interviews. Therefore, we need to total these three columns up to find all the applicents that went on fewer than 12. 3-5 went on 6, 6-8 went on 8, and 9-11 went on 5. Therefore, 6 + 8 + 5 = 19 applicents.
Just add the bar graphs that are before 12 interviews....6+5+8=19 applicants