From the scatterplot, estimate two points that the line of best fit passes through. The data runs approximately from $(5, 8)$ to $(30, 17)$.

The slope of the line of best fit is approximately:

$m \approx \frac{17 - 8}{30 - 5} = \frac{9}{25} = 0.36$

This is closest to $\dfrac{1}{3} \approx 0.33$.