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bonjour

5 x - 12 = 8

5 x = 8 + 12

5 x = 20

x = 4

3 x+ 22 = 26

3 x = 26 - 22

3 x = 4

x = 4 /3

39.3 + 2 x = 129.3

2 x = 129. 3 - 39.3

2 x = 90

x = 45

7 x - 2 =  1.5

7 x = 1.5 + 2

7 x = 3.5

x = 0.5  

Réponse :

bonjour

5x-12=8      

5x=8+12

5x=20

x=20/5=4

verifions 5×4-12=20-12=8

3x+22=26

3x=26-22

3x=4

x=4/3

vérifions 3×4/3+22=12/3+22=4+22=26

39.3+2x=129.3

2x=129.3-39.3

2x=90

x=90/2=45

vérifions 39.3+2×45=39.3+90=129.3

7x-2=1.5

7x=1.5+2

7x=3.5

x=3.5/7=1/2

vérifions

7×1/2-2=7/2-2=3.5-2=1.5

Explications étape par étape