Réponse :
bonjour
Explications étape par étape :
A = (+4) − (−5) + (+7) − [(+6) + (−9)]
=4+5+7-(6-9)
=16-(-3)
=16+3
19
B = (−18) + (−7) + (+12) + (+7) + (−4)
=-18-7+12+7-4
=-18-7-4 +12+7
=-29 +19
=-10
C = (−2,5) − (−3,4) – (-5,4) – (+7,2)
=-2.5+3.4+5.4-7.2
=-2.5-7.2+3.4+5.4
=-9.7 +8.8
=-0.9
D=4-9-[(-6 − 9) + (8 – 12)]
= 4-9 - (-15 + -4)
=-5 - (-11)
=-5+11
=6