SAT Question 2554b413: Linear Equations In Two Variables answer and explanation with Desmos solution

Choice A is correct. The slope-intercept form of an equation for a line is $y=mx+b$, where $m$ is the slope of the line and $b$ is the $y$-coordinate of the $y$-intercept of the line. It's given that the slope is $6$, so $m=6$. It's also given that the line passes through the point $(0,8)$ on the $y$-axis, so $b=8$. Substituting $m=6$ and $b=8$ into the equation $y=mx+b$ gives $y=6x+8$.