1st: A(11-7=4) B(7+7=14) C(6)
2nd: A(4) B(14-6=8) C(6+6=12)
3rd: A(4+4=8) B(8) C(12-4=8)
11, 7, 6
--> 4, 14, 6 (11-7 , 7+7 ,6 )
--> 4, 8, 12 ( 4, 14-6 , 6+6 )
--> 8, 8, 8 ( 4+4 , 8 , 12-4 )