(i) y = 3∵ y = 3 is an equation in one variable, i.e., y only.∴ y = 3 is a unique solution on the number line as shown below:(ii) y = 3We can write y = 3 in two variables as 0.x + y = 3Now, when x = 1, y = 3x = 2, y = 3x = -1, y = 3∴ We get the following table:Plotting the ordered pairs (1, 3), (2, 3) and (-1, 3) on a graph paper and joining them, we get aline AB as solution of 0. x + y = 3,i.e. y = 3.