tentukan nilai x dan y

Pers.1
2x + y = 9
y = 9 - 2x
Pers.2
x + 3y = 7
x + 3 (9 - 2x) = 7
x + 27 - 6x = 7
-5x = 7 - 27
-5x = -20
5x = 20
x = 20 /5
x = 4
Pers.1
y = 9 - 2x
y = 9 - 2(4)
y = 9 - 8
y = 1