If 3(x-y) = 27 and 3(x+y) = 243, then x is equal to = ?

Answer: Option C

$$\begin{array}{rl}& {\text{3}}^{x-y}=27=3^3\\ & \iff x-y=\mathrm{3........}(i)\\ & 3^{x+y}=243=3^5\\ & \iff x+y=\mathrm{5........}(ii)\\ & \text{On solving (i) and (ii) ,}\\ & \text{we get }x=4\end{array}$$