Question 7140
Sale price = original price - discount.  Let $x = original price.  20% = 0.2

$280 = $x - $0.2x
$280 = $x(1-0.2)
$280 = $0.8x  Divide both sides by 0.8
$350 = $x

Original price was $350.

Check:

$350 - 0.2($350)
$350 - $70 = $280