Solve the following pair of linear equations using a graph: $3x + 4y = 6$ and $3x + 4y = 19$.

(D) For the equation $3x + 4y = 6$:
$4y = 6 - 3x$
$y = \frac{6 - 3x}{4}$
If $x = -2$,$y = \frac{6 - 3(-2)}{4} = \frac{12}{4} = 3$.
If $x = 2$,$y = \frac{6 - 3(2)}{4} = \frac{0}{4} = 0$.

$x$	$-2$	$2$
$y$	$3$	$0$

Plot the points $(-2, 3)$ and $(2, 0)$ and join them to draw the line.
For the equation $3x + 4y = 19$:
$4y = 19 - 3x$
$y = \frac{19 - 3x}{4}$
If $x = 5$,$y = \frac{19 - 3(5)}{4} = \frac{4}{4} = 1$.
If $x = 1$,$y = \frac{19 - 3(1)}{4} = \frac{16}{4} = 4$.

$x$	$5$	$1$
$y$	$1$	$4$

Plot the points $(5, 1)$ and $(1, 4)$ and join them to draw the line.
Since the lines are parallel and do not intersect,the system of equations has no solution. The solution set is $\varnothing$.