FAST RESPON PLEASE. Tentukan subtitusi 3x-y=-7 , x+3y=1

3x - y = -7
-y = -3x - 7
y = 3x + 7

y = 3x + 7 disubstitusikan ke pers. 2
x + 3y = 1
x + 3 (3x + 7) = 1
x + 9x + 21 = 1
10x = 1 - 21
10x = -20
x = -20/10
x = -2

x = -2 disubstitusikan ke pers. 1
3x - y = -7
3(-2) - y = -7
-6 - y = -7
-y = -7 + 6
-y = -1
y = 1

HP = {-2, 1}