8x – 9y – 21 = 0
8x – 9y – 21 +21=0+21
8x – 9y =0+21
8x – 9y=21
3x – 2y - 12 = 0
3x – 2y-12+12=0+12
3x – 2y=0+12
3x – 2y=12
