Ada yang tau cara nya ? mohon penjelasan nya nomer6

3x + 2y = 0 ×1
x + 3y = 7 ×3

3x + 2y = 0
3x + 9y = 21
_________ _
-7y = -21
y = 3
x + 3(3) = 7
x = -2

2(-2) + 3 = -1 C