Respostas

2014-03-19T11:11:45-03:00
A +8+7=+15
b 9+3=12
c -10+5=-5
d -2-8=-10
e -9-12=-21
f -8+9=1
1 5 1
2014-03-19T11:12:22-03:00
A ) + 8 + 7 = 15
b ) 9 + 3 = 12
c ) -10 + 5 = -5
d ) -2 - 8 = -10
e ) -9 - 12 = -21
f ) -8 + 9 = 1 
2 4 2