4(1-2x)= 3(3-y)-12
4-8x=9-3y-12
-8x+3y=9-12-4
-8x+3y=-7
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2(3x-1)-(y+4)= -7
6x-2-y-4=-7
6x-y=-7+2+4
6x-y=-1 multiply by 3 & add
18x-3y=-3
-8x+3y=-7
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10x=-10
x=-10/10
x=-1 ans.
4(1-2*-1)=3(3-y)-12
4(1+2)=9-3y-12
4*3=-3-3y
12=-3-3y
3y=-3-12
3y=-15
y=-15/3
y=-5
Proof:
2(3*-1-1)-(-5+4)=-7
2(-3-1)-(-1)=-7
2*-4+1=-7
-8+1=-7
-7=-7
