**Q.1.** 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 x and that of a pen to be y).

**Solution:**

Let the cost of notebook be x and the cost of pen be y.

Then, ATQ,

Cost of a notebook = twice the cost of pen

⇒ x = 2y

⇒ x - 2y = 0