? % of 450 + 46% of 285 = 257.1

Answer: Option B

Let x% of 450 + 46% of 285 = 257.1
$$\Rightarrow \left(\frac{x}{100}\times 450\right)+\left(\frac{46}{100}\times 285\right)$$     $$=257.1$$
$$\begin{array}{rl}& \Rightarrow \frac{9x}{2}=257.1-131.1\\ & \Rightarrow \frac{9x}{2}=126\\ & \Rightarrow x=\frac{126\times 2}{9}\\ & \Rightarrow x=28\end{array}$$