So, to solve this problem you have to distribute on both sides. this would bring the equation to 3x+21=6x+12. You then can subtract 3x from both sides to bring the equation to 21=3x+12. Then, subtract 12 from both sides. The equation is now 9=3x. To isolate x, divide both sides by 3. This leaves you with x=3, so the solution to 3(x+7)=6(x+2) is x=3, or (3,0)
I hope this helps!
-Raiden
