If 'A' stands for ’÷’, 'B' stands for 'x', 'C' stands for ‘+’and 'D' stands for ‘- ’ what will come in place of the question mark (?) in the following equation?
42 A 7 B 13 C 87 D 12 = ?

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