Réponses

2013-10-13T21:09:57+02:00
Bonsoir

a/  -9) - (-3) - (+7)    = -9 +3 -7 = - 13
b/  (-15) + ( -24) - (+17) - (-21) = -15 -24 -17 +21 = - 35

2013-10-13T21:18:10+02:00
(-9) - (-3) - (+7)   
= -9+3-7
= -13  

(-15) + ( -24) - (+17) - (-21)
= -15-24-17+21
= -35