Answer is in the photo. I can't attach it here, but I uploaded it to a file hosting. link below! Good Luck!
tinyurl.com/wpazsebu
35 degrees
Triangles should typically add all up to 180 degrees
Since the price is going down, it's going to be a percent decrease. Now to find the percent, we divide the "after" price by the "before" price.
240 / 320 = 0.75 = 75%
The item had a 75% decrease.