Chapter 8 - Coordinate Geometry and Linear Systems - 8.1 - Cartesian Coordinate System - Problem Set 8.1 - Page 335: 21

$y=-\dfrac{3}{7}x+\dfrac{13}{7}$

Using the properties of equality, in terms of $ y ,$ the given expression, $ 3x+7y=13 ,$ is equivalent to \begin{array}{l}\require{cancel} 7y=-3x+13 \\\\ y=-\dfrac{3}{7}x+\dfrac{13}{7} .\end{array}