The cost of a notebook is twice the cost of a pen. Write a linear equation in two variables to represent this statement. (Take the cost of a notebook to be Rs. $x$ and that of a pen to be Rs. $y$).

(A) Let the cost of a notebook be Rs. $x$.
Let the cost of a pen be Rs. $y$.
According to the given condition,the cost of a notebook is twice the cost of a pen.
Therefore,we can write the equation as:
$x = 2y$
Rearranging the terms to the standard form of a linear equation in two variables $(ax + by + c = 0)$:
$x - 2y = 0$
Thus,the required linear equation is $x - 2y = 0$.