"Recall the definition of the slope of a line between two points: "
\quad "slope of line between" \ ( x_1, y_1 ) \quad "and" \quad ( x_2, y_2 ) \ = \ { y_2 - y_1} / { x_2 - x_1}.
"Applying this definition to our two given points, we get:"
\quad "slope of line between" \ ( 6, 0 ) \quad "and" \quad ( 0, -8 ) \ = \ { (-8) - (0) } / { (0) - (6) }
\qquad \qquad \qquad \qquad = \ { -8 } / { - 6 } \ = \ { (-2) (4) } / { (-2) (3) } \ = \ { color{red}cancel{ (-2) } (4) } / { color{red}cancel{ (-2) } (3) } \ = \ 4/3.
"So, we conclude:"
\qquad \qquad "slope of line between" \ ( 6, 0 ) \quad "and" \quad ( 0, -8 ) \ = \ 4/3 \ .