Hi,
Let's solve the equation step-by-step. 
x−3x=2(4+x) 
Step 1: Simplify both sides of the equation. 
x−3x=2(4+x) 
x+−3x=(2)(4)+(2)(x)(Distribute) 
x+−3x=8+2x 
(x+−3x)=2x+8(Combine Like Terms) 
−2x=2x+8 
−2x=2x+8 
Step 2: Subtract 2x from both sides. 
−2x−2x=2x+8−2x 
−4x=8 
Step 3: Divide both sides by -4. 
−4x/−4 = 8/−4 
x=−2 
Answer: 
x=−2
Have a great day!