Metode subtitusi B. X+4y=0 dan 2x+y=7

x+4y = 0, x = -4y atau y = -x/4

2x+y = 7
2(-4y)+y = 7
-8y +y = 7
-7y = 7
y = -1

2x+y = 7
2x+(-x/4) = 7
2x-x/4 = 7
8x-x/4 = 7
7x / 4 = 7
7x = 28
x = 4