First multiply both sides by 3
• 3x + 12= 12x -15
Second move the variable to the left side and change its sign:
• 3x + 12 -12x = -15
Third move constant to the right side and change its sign:
• 3x -12x = -15 -12
Fourth collect like terms:
• -9x= -27
Last divide both side by -9:
• x= 3
So the value of x is 3