To find the slope of a line given two points on that line, the difference between the y values must be divided by the x values.
Line 1:
0 - -3 = 3
8 - -4 = 12
3/12 = 1/4 (slope)
Line 2:
6 - 2 = 4
-1 - 0 = -1
4/-1 = -4 (slope)
Line 3:
-7 - -4 = -3
6 - -3 = 9
-3/9 = -1/3 (slope)
The slope of lines 1 and 2 are perpendicular. For slopes to be perpendicular, the numerators and denominators must be switched and the signs need to be opposite.
The slope of lines 1 and 3 are neither parallel nor perpendicular.
The slope of lines 2 and 3 are neither parallel nor perpendicular.