Efectuați:
a) (-7)+(+3)=;
d) (-3)+(+12) = ;
g) (+13)+(-2) =;
j) (+7)H-13)=;
b) (-9)+(+5) = ;
e) (-8)+(+9) = ;
h) (+9)+(4) = ;
k) (+5)+(-5) =;
c) (-12)+(+7)=;
f) (-7)+(+7) = ;
i) (+20)+(-18) = ;
1) (+12)+(-13) = .​