Question 66734
5x-4y=20

Start by putting this equation into y=mx+b:

5x-4y=20
Subtract 5x:
-4y=-5x+20
Divide by -4:
y=5/4x-5

Now that your equation is in y=mx+b, you can easily identify the slope, or m. Since m is 5/4, that is your slope. Remember the slope of perpendicular lines is the negative reciprocal. Therefore, the slope of the perpendicular line is-4/5. y=-4/5-5 is the equation of the perpendicular line.