If 91% of A is 39% of B, and B is x% of A, then the value of x is:

Answer: Option C

$$\begin{array}{rl}& 91\%\text{ of }A=39\%\text{ of }B\\ & \frac{91}{100}\times A=\frac{39}{100}\times B\\ & B=\frac{91}{39}A\\ & B=x\%\text{ of }A\\ & \frac{91}{39}\times A=\frac{x}{100}\times A\\ & x=\frac{91}{39}\times 100=\frac{700}{3}\end{array}$$