Explanation:
x+y=12
3×+y=20
×=12-y
3 (12-y)+y=20
36-3y+y=20
36-4y=20
-4y=20-36
-4y= -16
y =16÷4
y=4
×+y=12
×+4=12
×=12-4
×=8
therefoer;y=4,x=8
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