Chapter 2 - Functions, Equations, and Graphs - 2-4 More About Linear Equations - Practice and Problem-Solving Exercises - Page 86: 23

$7x+y=-9$

Recall: The standard form of a line's equation is $Ax+By=C$. where $A, B, $ and $C$ are real numbers and $A$ and $B$ cannot be both zero. Add $7x$ to both sides of the given equation to obtain: \begin{align*} y+7x&=-7x-9+7x\\ 7x+y&=-9 \end{align*}