Here's a bit of mental floss [1] for your otherwise slothful weekend. I had a hard time with 8, 10, and 17 (good guesses, but not the right ones).ÂÂ
[2]
Links:
[1] http://thehindsightfactor.com/files/Puzzles.rar
[2] http://www.addtoany.com/share_save?linkurl=http%3A%2F%2Fthehindsightfactor.com%2Fweekend_brain_teasers&linkname=Weekend%20Brain%20Teasers