Bonjour,

x/2 = 4,5

x = 4,5 * 2

x= 9

2x-1 = 8-x

2x+x =  8+1

3x = 9

x= 9/3

x= 3

2(x-1)  = 8+2x

2x-2 = 8+2x

2x-2x = 8+2

???

-3( x-1) +x = 3-2x

-3x +3 +x = 3-2x

-2x +3 = 3-2x

-2x +2x = 3-3

0 = 0