Writing numbers: Cardinals for Quantities and Ordinals for Dates and orders

Can you write 9999 (nine thousand nine hundred ninety-nine) in full? Why do numbers in dates end in 'th' or other strange letters (e.g.: June 12th)? If your answer is 'no' or 'I don't know', you'd better check out this exercise and get some tips. Return it to the teacher for correction and scoring.