The answers to the questions are:
- The correct solution to the equation is \(x = \frac{43}{6}\).
- The method Karen used is option 4: add \(x + 5x\), subtract \(7\) from both sides of the equation.
- The binomial expression is \(3 + 4x\).
Thus, the final answers are:
\[
\boxed{x = \frac{43}{6}}
\]
\[
\text{Correct method: Option 4}
\]
\[
\text{Binomial expression: } 3 + 4x
\]