What will come in place of '?' in the following equation, if '+' and '÷' are interchanged and '×' and '-' are interchanged?
12 - 6 ÷ 3 + 3 × 7 = ?

Given: 

12 - 6 ÷ 3 + 3 × 7 = ?

'+' and '÷' are interchanged

'×' and '-' are interchanged

​$$\begin{array}{|c|c|} \hline\textbf{Operation preference wise} & \textbf{Symbol} \\\hline\text{Brackets} &[],{}, () \\ \hline \text{Orders, of} & (power), √ (root) , of \\ \hline \text{Division}& ÷ \\ \hline \text{Multiplication} & × \\\hline \text{Addition} & + \\ \hline \text{Subtraction} & -\\\hline\end{array}$$​​

12 - 6 ÷ 3 + 3 × 7 = ?

After interchange the sign we get following equation - 
12 × 6 + 3 ÷ 3 - 7 = ?
72 + 1 - 7 = ?
73 - 7 = ?
66 = ?

Correct answer is (a) 66.