Bài làm :
\(12x+3\left(x-1\right)=27\)
\(12x+3x-3=27\)
\(15x=30\)
\(x=30:15\)
\(x=2\)
Học tốt nhé
\(12x+3\left(x-1\right)=27\Rightarrow3.4x+3\left(x-1\right)=27\Rightarrow3[4x+\left(x-1\right)]=27\)\(\Rightarrow4x+\left(x-1\right)=27:3\Rightarrow4x+x-1=9\Rightarrow x\left(4+1\right)=10\)\(x.5=10\Rightarrow x=2\)
12x + 3(x - 1) = 27
12x + 3.x - 3.1 = 27
12x + 3x - 3 = 27
15x -3 = 27
15x = 27 + 3
15x = 30
x = 30 : 15
x = 2