A house was sold for Rs. y by giving a discount of x% , then the list price was = ?

Answer: Option C

$$\begin{array}{rl}& \text{Discount}=x\%\\ & \Rightarrow \text{Selling price}=\text{Rs}\text{.}y\\ & \Rightarrow \text{MRP}=?\\ & \Rightarrow \text{MRP}\times \left(100-x\right)\%=y\\ & \Rightarrow \text{MRP}=\frac{y}{\left(100-x\right)\times \frac{1}{100}}\\ & \Rightarrow \text{MRP}=\text{Rs}.\frac{100y}{\left(100-x\right)}\end{array}$$