Draw the graph of the linear equation in two variables: $x + y = 4$.

(N/A) $x + y = 4$
$\Rightarrow y = 4 - x$
If we have $x = 0$,then $y = 4 - 0 = 4$.
If we have $x = 1$,then $y = 4 - 1 = 3$.
If we have $x = 2$,then $y = 4 - 2 = 2$.
$\therefore$ We get the following table:

$x$	$0$	$1$	$2$
$y$	$4$	$3$	$2$

Plot the ordered pairs $(0, 4)$,$(1, 3)$,and $(2, 2)$ on the graph paper. Joining these points,we get a line $AB$ as shown in the graph. Thus,the line $AB$ is the required graph of $x + y = 4$.