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

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

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

Give the equations of four lines passing through $(2,3)$.

State whether the following statement is True or False and justify your answer:
Every point on the graph of a linear equation in two variables does not represent a solution of the linear equation.

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