If 3(x+y) = 81 and 81(x-y) = 3, then the value of x is = ?

Answer: Option C

$$\begin{array}{rl}& {\text{3}}^{x+y}\text{ = 81}\\ & {\text{3}}^{x+y}\text{ = }{\text{3}}^4\\ & x+y=\mathrm{4.....}(i)\\ & \text{8}{\text{1}}^{x-y}\text{ = 3}\\ & 3^{4x-4y}\text{ = }{\text{3}}^1\\ & 4x-4y\text{ = 1}....\text{(ii)}\\ & \text{From equation (i) and (ii)}\\ & 4x-4y=1\\ & 4x+4y=16\\ & 8x=17\\ & x=\frac{17}{8}\end{array}$$