How do you find the slope of -5x+3y-8=0

you could change it to the form y = mx +b,

requiring at least two steps:

-5x+3y-8=0

3y = 5x+ 8
y = (5/3)x + 8/3
so the slope is 5/3

Here is a quick little algorithm which I suggest you memorize.
If the equation is in the form Ax + By = C
or Ax + By + C = 0
the slope = -A/B

so for yours above, slope = -(-5)/3 = 5/3
and you can do them in your head.
Notice the constant has no effect on the slope.