( 4 + 3 ) + 2 = 7 + 2 = 9
( 15 - 9 ) - 5 = 1
( 6 + 4 ) + 7 = 10 + 7 = 17
( 11 - 5 ) - 4 = 6 - 4 = 2
( 12 - 8 ) + 8 = 4 + 8 = 12
( 4 + 3 ) + 2 = 7 + 2 = 9
( 15 - 9 ) - 5 = 1
( 6 + 4 ) + 7 = 10 + 7 = 17
( 11 - 5 ) - 4 = 6 - 4 = 2
( 12 - 8 ) + 8 = 4 + 8 = 12