pke cara substitusi...please bwt temen saya...

1.
x + y = 3
2x + y = 12

x + y = 3
x = 3 - y

2x + y = 12
2(3 - y) + y = 12
6 - 2y = 12
- 2y = 12 - 6
- 2y = 6
y = - 3

x = 3 - y
x = 3 + 3
x = 6

2.
x - y = 4
3x + 3y = - 12

x - y = 4
x = 4 + y

3x + 3y = - 12
3(4 + y) + 3y = - 12
12 + 3y + 3y = - 12
6y = - 12 - 12
6y = - 24
y = - 4

x = 4 + y
x = 4 - 4
x = 0

3.
2x - y = 3
y = 1

2x - y = 3
2x - 1 = 3
2x = 3 + 1
2x = 4
x = 2

4.
x + 3y = 5
x = 2

x + 3y = 5
2 + 3y = 5
3y = 5 - 2
3y = 3
y = 1

5.
2x + y = 4
x + y = 1

x + y = 1
x = 1 - y

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

x = 1 - y
x = 1 + 2
x = 3

Maaf Kalau Salah