Question

Give geometric representation of $y = 3$ as an equation in one variable.

Given equation in one variable is $y = 3$
As we know that the equation of any straight line is $y = mx + c$ where $m$ is the slope of that line and $c$ is the y-intercept of the line.
If we compare the given equation with the equation of any straight line, we can say that the given equation in one variable is the equation of a straight line with a slope of zero and y-intercept as 3 which means the given straight line is cutting the y-axis at $\left[ {0,3} \right]$.
The geometrical representation of $y = 3$ as an equation in one variable is shown in the below figure.