Respostas

2014-05-09T23:18:31-03:00
A) (+5)+(+7)= 5 +7=12
B) (-9)-(-3)= -9+3= -6
C) (+15) - (+7)+(-2)= 15 -7 -2= 15 -9= 6
D) (-2)+(-4)=-2 -4= -6
E) (-9)+(13)+(5)= -9+13+5= -9 +18= 9