ok so basically, you are going to use the distributive property to solve this problem.
First, Use the distributive property.
So basically 3(x + 4) = 9 would be:
3x + 12 = 9 after the distributive property
Then you subtract 12 from both sides
3x = -3
Then you divide 3 by both sides
you will get x = -1
Hope this helps
Here is an image to make my work clearer