# How do you find the slope of a line perpendicular to 3x+10y=-20?

$y = - \frac{3}{10} x - 2$ (I isolated $y$ on one side)
here you can "read" the slope $m$ of your line which is $m = - \frac{3}{10}$ (the coefficient of $x$);
Now, the line perpendicular will have slope ${m}_{1} = - \frac{1}{m}$
or: ${m}_{1} = \frac{10}{3}$