To find the slope, we can use the formula m = y change/x change. Since we already have 2 points, we can subtract the second coordinates from the first ones.
1. (-18-(-18))/(15-6) = 0/9 = 0. m=0x
2. (16-12)/0-8) = 4/-8 = -1/2. m = -1/2x
Hope this helps.
