Invalid question. You cannot find the slope with just y=-12.
The slope is -6 and the y intercept is 12
Point slope equation: Y=3X+12
2x + 3y = 12
y = -2/3 y + 4
slope is -2/3
[ y = 12x ] is an equation, not a 'problem'.
The graph of that equation is a straight line with a slope of 12