In Rhino you can start drawing a line, setting one endpoint, and then specify an angle in degrees by first typing in the angle like:
< 45 [ENTER]
…for 45-degrees. The line will snap to your angle.
You can use either a formula, or an online calculator such as this for converting the slope.
I don’t work with slopes, and rarely seem specified in mechanical contrivances, but in the context, they would seem a percentage of 90 degrees, but apparently, they are a percentage of 45 degrees?