We have to find the slope of the following equation

$$ x+5y=9 $$

$$ 5y=-x+9 $$

$$ y=-\frac{1}{5}x+\frac{9}{5}.............(1) $$

We know that the equation of slope is

$$ y=mx+c................(2) $$

where,

$$ m=\frac{a}{b} $$

So comparing equation (1) with (2), we have

$$ slope=m=-\frac{1}{5} $$