If 5#3@3=12 and 7 # 2 @ 4 = 10, then what will be 2 # 9 @ 5?

If ‘A’ stands for ‘÷’, ‘B’ stands for ‘×’, ‘C’ stands for ‘+’ and ‘D’ stands for ‘–’, what will come in place of the question mark (?) in the following equation?
23 B 4 D 45 A 9 C 11 = ?

If ‘A’ stands for ‘÷’, ‘B’ stands for ‘×’, ‘C’ stands for ‘+’ and ‘D’ stands for ‘−’, then the resultant of which of the following would be 77?​

If ‘A’ stands for ‘÷’, ‘B’ stands for ‘×’, ‘C’ stands for ‘+’ and ‘D’ stands for ‘−’, then the resultant of which of the following would be 75?​

If ‘P’ stands for ‘×’, ‘Q’ stands for ‘÷’, ‘R’ stands for ‘−’ and ‘S’ stands for ‘+’, then what will come in place of the question mark (?) in the following equation?
(110 R 32) Q 2 S 9 P 4 R 21 = ?