X + Y = 12 X - Y = 4

x + y = 12
x - y = 4
--------------- -
2y = 8
y = 8/2
y = 4

x + y = 12
x + 4 = 12
x = 12 -4
x = 8

Semoga membantu dan semoga bermanfaat...

x + y = 12
x - y = 4
_______ +
2x = 16
x = 16/2 = 8

x + y = 12
8 + y = 12
y = 12-8 = 4