If the graph of the equation $ax + 3y = 21$ passes through the point $(5, 2)$,then the value of $a = \ldots$

$A$ linear equation in two variables has how many solutions?

The following observed values of $x$ and $y$ are thought to satisfy a linear equation. Write the linear equation:

$x$	$6$	$-6$
$y$	$-2$	$6$

Draw the graph using the values of $x$ and $y$ as given in the above table.
At what points does the graph of the linear equation:
$(i)$ cut the $x$-axis and
$(ii)$ cut the $y$-axis?

How many solution$(s)$ of the equation $2x + 1 = x - 3$ are there on the:
$(i)$ Number line
$(ii)$ Cartesian plane

Express the following linear equation in the form $ax + by + c = 0$ and indicate the values of $a, b$ and $c$ in each case:
$5x + 3y = 45$

The graph of the equation $0x + 3y = 21$ is perpendicular to which axis?