Which two signs should be interchanged to make the below equation mathematically correct?
9 ÷ 3 + 6 – 6 × 2 = 30

Given: 9 ÷ 3 + 6 – 6 × 2 = 30

Used BODMAS rule.

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

Now, we check each options.

Option (a): + and ÷

New equation: 9 + 3 ÷ 6 – 6 × 2 = 30

12 ÷ 6 - 6 × 2 = 30

2 - 6 × 2 = 30

- 10 $$\neq$$ 30​

Option (b): × and ÷

New equation: 9 × 3 + 6 – 6 ÷ 2 = 30

9 × 3 + 6 - 3 = 30

27 + 6 - 3 = 30

33 - 3 = 30

Option (c): + and -

New equation: 9 ÷ 3 - 6 + 6 × 2 = 30

3 - 6 + 6 × 2 = 30

3 - 6 + 12 = 30

9 $$\neq$$ 30​

Option (d): × and +

New equation: 9 ÷ 3 × 6 – 6 + 2 = 30

3 × 6 - 6 + 2 = 30

18 - 6 + 2 = 30

14 $$\neq$$ 30​

Thus, correct option is (b).