Răspuns :

2(x+3)-5(2x+1)=12x-9
2x+6-10x-5=12x-9
-8x+1=12x-9
20x=10
x=10/20
x=1/2
2(x+3)-5(2x+1)=12x-9
2x+6-10x-5=12x-9
2x-10x-12x=-9-6+5
-20x=-10 (inmultim cu -1 ambele parti)
20x=10
x=10/20
x=1/2=0.5