Which two numbers, from amongst the given options, should be interchanged to make the given equation correct?

What will come in the place of the question mark ‘(?)’ in the following equation, if ‘+’ and ‘−’ are interchanged and ‘×’ and ‘÷’ are interchanged?
116 ÷ 5 − 423 × 3 + 13 = ?​

Which of the following equations is correct when the numbers 12 and 6 are interchanged and the signs ÷ and + are interchanged?

Which of the following equations is correct when the numbers 3 and 9 are interchanged and the signs - and × are interchanged?

If 'p' means '×', 'q' means '-', 'r' means '÷' and 's' means '+', then which of the following equation is NOT correct?
I. 44 s 51 r 17 q 20 p 4 = -31
II. 57 r 19 s 5 p 10 q 18 = 35

If 'P' stands for 'x', 'Q' stands for '÷', 'R' stands for '-' and 'S' stands for '+', then the resultant of which of the following would be 57?