If 1-3+4=100, 4-6+9=999, 2-6+7=879 then 3-3+6=?

Question

Answer 1

1•a-3•b+4•c=100 (1)
4•a-6•b+9•c=999 (2)
2•a-6•b+7•c=879 (3)

(1)x3, get
2•a-6•b+8•c=200 (4)

(4)-(3), get
c=-679

(2)-(3), get
2•a+2•c=120
a=[120-2•(-679)]/2=739

substitute value a & c to (1), get
-3•b=100-1•(739)-4•(-679)=2077

3•a-3•b+6•c
=3•(739)+2077+6•(-679)
=220

3-3+6=220

Answer 2

answer is 220

Comments

What is the logic????

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