If 9 Δ 2 = 7 and 6 Δ 3 = 3, then what is the value of 5 Δ 1?

If '+' is interchanged with '-' and '×' is interchanged with '÷', what will come in place of '?' in the following equation? 529 ÷ 23 + 89 - 12 × 9 = ?

By interchanging which two signs will the given equation become correct? 15 - 9 ÷ 6 × 10 + 5 = 25