Question

-2001+(1999+2001)

Answer 1

-2001+1999+2001

=[-2001+2001] +1999

=0+1999=1999

Answer 2

-2001+(1999+2001)=-2001+1999+2001=(-2001+2001)+1999=0+1999=1999

Answer 3

 -2001+(1999+2001) 

= -2001 + - 2001 + 1999

= 0                      + 1999

= 1999

Answer 4

2001 + { 1999 + 2001}

= 2001 + 4000

= 6001