The cost of a notebook is twice the cost of a pen. Write a linear equation in two variables to represent this statement.

Let the cost of a notebook be Rs. x and cost of a pen be Rs. y.
According to the question, the cost of a notebook is twice the cost of a pen.
∴ x=2y
⇒x - 2y=0
Hence, x - 2y = 0 is the equation in two variables that represent the given statement.