## Geometry: Common Core (15th Edition)

$\frac{1}{3}$
The equation of the line is already in slope-intercept form, which is given by the following formula: $y = mx + b$, where $m$ is the slope of the line and $b$ is the y-intercept of the line. Looking at the equation $y = -3x + 4$, we see that $m = -3$, but we are looking for a perpendicular line to this one. Perpendicular lines have slopes that are negative reciprocals of one another. This means that the product of their slopes equals $-1$. The negative reciprocal of $-3$ is $\frac{1}{3}$.