## Intermediate Algebra (6th Edition)

$180-x$
You are told that the sum of two angle measures (which we will call $x$ and $y$) is 180 degrees. Therefore, $x+y=180$. To isolate $y$ and determine its value in terms of $x$, you need to subtract $x$ from both sides. $(x+y)−x=180−x$ Therefore, $y=180−x$.