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.

For each of the graphs given in the figure,select the equation whose graph it is from the choices given below:
$(a)$ For Fig. $(i)$,
$(i)$ $x+y=0$ (ii) $y=2x$ (iii) $y=x$ (iv) $y=2x+1$
$(b)$ For Fig. (ii),
$(i)$ $x+y=0$ (ii) $y=2x$ (iii) $y=2x+4$ (iv) $y=x-4$
$(c)$ For Fig. (iii),
$(i)$ $x+y=0$ (ii) $y=2x$ (iii) $y=2x+1$ (iv) $y=2x-4$

Any point on the line $y=x$ is of the form

If the point $(3, 5)$ lies on the graph of the equation $ax + y = 20$,find the value of $a$.

In a Cartesian plane,the graph of the equation $y=5$ is parallel to the ........ axis.

Draw the graph of the equation represented by a straight line which is parallel to the $x$-axis and at a distance of $3$ units below it.