Respostas

2013-06-04T11:04:34-03:00

(-5)+2+1-7=

-5+3-7=

12-3=

=9

 

B)2+3-5+9=

    14-5=

=9

2013-06-04T11:05:16-03:00

(-5)+(+2)-(-1)+(-7)      

-5+2+1-7=

-3+1-7=

-2-7=

-9

 

(+2)-(-3)+(-5)-(-9)

+2+3-5+9=

+5-5+9=

0+9=

+9