b) -23 . 63 + 23 . 21 - 58 . 23
= -1449 + 483 - 1334
= -2300
c) -2003 + ( -21 + 75 + 2003 )
= -2003 -21 +75 + 2003
= 54
e) 12 - 12 + 11 + 10 - 9 + 8 - 7 + 5 - 4 + 3 + 2 -1
= 12 - ( 12 - 11 ) + ( 10 - 9 ) + ( 8-7) + ( 5-4 ) + 3 + ( 2 -1 )
= 12 - 1 + 1 + 1 + 1 + 3 + 1
= 18