3. If the number 1 on the clock is replaced by the letter M, the number 2 is replaced by N and so on, then when the time is 21:00 p.m. the hour hand will be at ____ letter
5. In a certain code language, '+' represents 'x', '-' represents '+', 'x' represents '÷' and '÷' represents '-'. What is the answer to the following question? 50 + 3 ÷ 125 x 5 - 25 = ?