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 = ?

Given: 

(110 R 32) Q 2 S 9 P 4 R 21 = ?

Given equation is solve by BODMAS rule.

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

New equation: (110 - 32) $$\div$$​ 2 + 9 $$\times$$​ 4 - 21 = ?

78 ÷  2 + 9 $$\times$$​​ 4 - 21 = ?

39 + 36 - 21 = ?

75 - 21 = ?

? = 54

Thus, correct option is (c).