SAT Question 8a1544f1: Linear Equations In Two Variables answer and explanation with Desmos solution

Choice B is correct. Any line in the $xy$-plane can be defined by an equation in the form $y=mx+b$, where $m$ is the slope of the line and $b$ is the $y$-coordinate of the $y$-intercept of the line. From the graph, the $y$-intercept of the line is $(0,3)$. Therefore, $b=3$. The slope of the line is the change in the value of $y$ divided by the change in the value of $x$ for any two points on the line. The line shown passes through $(0,3)$ and $(1,0)$, so $m=\frac{3-0}{0-1}$, or $m=-3$. Therefore, the equation of the line is $y=-3x+3$.