Give the geometric representations of y = 3 as an equation 

(i) in one variable 

(ii) in two variables

(i) y = 3

 y = 3 is a unique solution on the number line as shown below:
 

(ii) y = 3

We can write y = 3 in two variables as 0.x + y = 3

Now, for x = 1, y = 3

For x = 2, y = 3

For x = -1, y = 3
 

On plotting the points (1, 3), (2, 3) and (-1, 3) on a graph paper and joining them, we get a line AB as solution of 0. x + y = 3, i.e. y = 3.