tolong ya... soalnya besok dikumpul jalannya terserah mau pke subtitusi,eleminasi atau campuran

Correct me if i wrong :v

1. x + 5 = 3x - 7
5 + 7 = 2x
12 = 2x
x = 6, y = 11

2. x = 5 - y
2x + 3y = 7
2 (5 - y) +3y = 7
10 - 2y +3y. = 7
10 + y = 7
y = -3, x = 8

3. x + y = 2 - y
2y - 7 = 2 - y
3y = 9
y = 3

4. y = -x + 3
x - y = 5
x - (-x + 3) = 5
x + x - 3 = 5
2x = 8
x = 4, y = -1