Answer: D, 50
y = kx y = 20 and x = 0.4
What you will do: You will plug in your y and your x.
Your equation should look like: 20=k(0.4)
Next: What you will do is divide each side of your equal sign by 0.4 so you will get your k alone.
You would get: k=50
HOPE THIS HELPS! ^_^
