a) - 7 + ( - 5 + 5 ) = - 7 + 0 = - 7
b) - 4 + ( 4 - 8 ) = - 4 - 4= - 8
c) - 4509 + 2315 + 4509 = 2315
d) 123 - ( 117 - 0 ) + ( - 123 ) + 118 = - 117 + 118 = 1
e) 135 - 143 - ( 135 - 143 ) + 1 = 135 - 143 + 8 + 1 = 144 - 143 = 1
f) - 6 - [ 2 + ( - 8 ) + 0 ] = - 6 - ( 2 - 8 ) = - 6 + 6 = 0