Let's solve the equation step-by-step.
- We start with the last derived equation you provided:
\[ x = -6x + 21 \]
- Now, we want to add \(6x\) to both sides of the equation to get all the \(x\) terms on the left side:
\[ x + 6x = -6x + 21 + 6x \]
- This simplifies to:
\[ 7x = 21 \]
- From here, we can solve for \(x\) by dividing both sides by 7:
\[ x = \frac{21}{7} \]
- Therefore, we find:
\[ x = 3 \]
So, after adding \(6x\) to both sides and simplifying, we have found \(x = 3\).