You can divide your equation by 12 to put it into intercept form. Then read the intercepts from the equation.
.. (2x/12) + (-3y)/12) = 1
.. x/6 + y/-4 = 1
The x-intercept is 6
The y-intercept is -4
The "slope triangle" is 4 units high and 6 units wide, so ...
.. the slope is m = 4/6 = 2/3.
