4. In a certain code language, '+' represents 'x', '-' represents '+', 'x' represents '÷' and '÷' represents '-'. What is the answer to the following question? 80 + 2 ÷ 25 + 5 - 10 = ?
7. In a certain code language, '+' represents 'x', '-' represents '+', 'x' represents '÷' and '÷' represents '-'. What is the answer to the following question? 80 x 16 ÷ 4 + 2 - 8 = ?
9. In a certain code language, '-' represents 'x', '÷' represents '+', '+' represents '÷' and 'x' represents '-'. Find out the answer to the following question. 12 - 6 + 4 x 10 ÷ 16 = ?