Line 1= undefined
Line 2= -4/3
Line 3= 4/3
Line 4= undefined
Line 5= 7/3
Line 6= -7/3
Line 7=no slope
Line 8=no slope
Line 9 =undefined
Line 10 = undefined
Line 11 = no slope
Line 12= undefined
NOTE: if the line is horizontal it have a zero slope or no slope and a vertical line the slope is undefined.