Thank you for the opportunity to help you with your question!

When simplifying expressions, you should group the similar terms together. That means all the "x" terms are grouped together, and all the integers are grouped together. You should get this:

(-3x-6x) -1.

*Note: remember that the negative sign in front of (6x+1) gets distributed to both terms, so it becomes -6x -1 !!

Now, you simplify further to get -9x -1.

Please let me know if you need any clarification. I'm always happy to answer your questions. Good luck!