a, 20 - | -46 | + ( -25 ) - ( -46 )
= 20 - 46 - 25 + 46
= ( 20 - 25 ) + ( 46 - 46 )
= - ( 25 - 20 )
= -5
b, 5 - ( 1997 - 2020 ) + 1997
= 5 - 1997 + 2020 + 1997
= ( 5 + 2020 ) + ( 1997 - 1997 )
= 2025
c, 16 . ( -9 ) . ( -7 ) . [ - ( +13 ) + | -13 |]
= 16 . 9 . 7 . ( -13 + 13 )
= 16 . 9 . 7 . 0
= 0