( 51 + 29 ) - 30 = 80 - 30 = 50
( 67 + 7 ) - 27 = 74 - 27 = 47
( 67 + 7 ) + 27 = 67 + 7 + 27 = 101
43 + 9 + 11 + 7 + 30 = ( 43 + 7 ) + (11 + 9)+30 = 50 +20 + 30 = 100