Mathematical Operations Questions

In a certain code language, '+' represents 'x', '-' represents '+', 'x' represents '÷' and '÷' represents '-'. What is the answer to the following question?
642 x 6 ÷ 25 + 4 = ?

Select the number which can be placed in the place of ?

In a certain code language, '-' represents'+', '+' represents 'x', 'x' represents '÷' and '÷'represents '-'. Find out the answer to the following question.

2 - 12 + 10 x 5 ÷ 12 = ?

If the signs + and / and the numbers 2 and 4 are interchanged, which one of the following four equations would be correct?

In the following question, select the number which can be placed at the sign of ? from the given alternatives.

Find the missing number in the given question/

If "÷" denotes "multiplied by", "+" denotes "subtracted from", "x" denotes "added to" and "–" denotes "divided by",then

12 – 6 + 28 x 3 ÷ 9 = ?