I am not sure what to round it to because that part of the question was cut off in the picture, but the answer is

or
Here's the math:
Step 1.) Distribute the 6 across it's parenthesis and the 3 across its parenthesis
Step 2.) Combine like terms
Step 3.) Subtract 3x from both sides
Step 4.) Subtract 30 from both sides
Step 5.) Divide both sides by 21
Step 6.) Simplify the fraction with the GCF of 3

It is asking for a decimal though, so to find that, we divide -1 ÷ 7
= -0.142857
Thank you for your question! I hope this helped! Have an amazing day! :D