We have two hundred and twenty four employees.
The question demands the proper way to use words or numerals to express numbers.
Firstly, the apostrophe is not written before the "s" in 40s.
In the second statement, the number should have been written in words.
Thirdly in expressing time, "one" should have been written in numeral and not in words.
The last expression; The meeting starts at one o'clock. We have two hundred and twenty four employees is properly written.