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Meilleure réponse !
2014-04-28T14:51:00+02:00
A.0,9x=130
a.0,9x/0,9=130/0,9
a.x≈144,4

b.0,2x+80=130
b.0,2x=130-80
b.0,2x=50
b.0,2x/0,2=50/0,2
b.x=250

c.0,9x=45+0,4x
c.0,9x-0,4x=45
c.-0,5x=45
c.-0,5x/-0,5=45/-0,5
c.x=-90

d.0,2x+80=45+0,4x
d.0,2-0,4x=45-80
d.-0,2x=-35
d.-0,2x/-0,2=-35/-0,2
d.x=175
2014-04-28T15:07:28+02:00
Bonjour

0.9x = 130
x = 144.44

0.9x = 45 + 0.4x
0.9x - 0.4x = 45
0.5x = 45
x = 90

0.2x +80 = 130
0.2x = 130 -80
0.2x = 50
x = 250

0.2x +80 = 45 +0.4x
0.2x - 0.4x = 45 -80
-0.2x = 35
-x = 175
x = -175