1. The question asks about the origin of the term $7x$ in step 4. 2. Typically, $7x$ appears from combining like terms or distributing a coefficient in an algebraic expression. 3. For example, if you have $3x + 4x$, adding these like terms results in $7x$. 4. Alternatively, if you distribute a 7 over $x$, such as $7 \times x$, you get $7x$. 5. Without the exact previous steps, the most common source of $7x$ is the sum of terms involving $x$ or distribution of 7 to $x$. 6. If you provide the full step 4 or the equation, I can explain precisely how $7x$ was derived.