In an otherwise very simple puzzle, I can't see why my answer to 22d is correct. Can s'one perhaps give a HINT without the solution itself? Clue is:
3.15 (6 letters)
I won't even give the crossers. It has nothing to do with the answers numbered 3 & 15 in the puzzle.
Perhaps some clever mathematician can parse it nevertheless??!! I repeat, only a HINT please!!!