State whether the following statement is true or false:
In a Cartesian plane,the graph of $3x = 15$ is a line parallel to the $x$-axis.

If the point $(2, 3)$ lies on the graph of the equation $3x + ay = 18$,find the value of $a$.

The graph of the linear equation $y = x$ passes through the point.

Write whether the following statements are True or False? Justify your answers.
$(i)$ The line parallel to the $y$-axis at a distance of $4$ units to the left of the $y$-axis is given by the equation $x = -4$.
$(ii)$ The graph of the equation $y = mx + c$ passes through the origin.

Draw the graph of the linear equation $3x + 4y = 6$. At what points does the graph cut the $x$-axis and the $y$-axis?

The total cost of $3$ sweetlimes and $6$ oranges is ₹ $210$. Show this statement as a linear equation in two variables.