First, you would need to determine the discount amount.
$550 - $440 = $110
Next, you would need to create an equation for this problem. Let x represent the unknown percent discount.
[tex] \frac{110}{550} [/tex] = [tex] \frac{x}{100} [/tex]
Cross multiply.
550x = 11,000
Now, all you would need to do is isolate the x. To do this, you would divide both sides of the equal sign by 550.
x = 20
x = 20%
The percent discount was 20%.
I hope this helps!