Chapter 1 - Graphs - 1.3 Lines - 1.3 Assess Your Understanding - Page 30: 41

$y=-x+2$ or $x+y=2$

Step 1. Given two points $(-1,3),(1,1)$, we can find the slope $m=\frac{3-1}{-1-1}=-1$. Step 2. Use either point (2nd point used here), we can write the equation as $y-1=-(x-1)$ or $y=-x+2$ or $x+y=2$