The formula for determine the price of an item after a discount is applied is:
#s = p - (p * d)#
Where:
#s# is the sales price of the item: $280 for this problem.
#p# is the regular price of the item: $300 for this problem.
#d# is the discount percent of the sale: what we are solving for in this problem.
Substituting and solving for #d# gives:
#$280 = $300 - ($300 * d)#
#$280 - color(red)($300) = $300 - color(red)($300) - ($300 * d)#
#-$20 = 0 - ($300 * d)#
#-$20 = -$300 * d#
#(-$20)/color(red)(-$300) = (-$300 * d)/color(red)(-$300)#
#(-$2)/color(red)(-$30) = (color(red)(cancel(color(black)(-$300))) * d)/cancel(color(red)(-$300))#
#(-color(red)(cancel(color(black)($)))2)/color(red)(-color(black)(cancel(color(red)($)))30) = (color(red)(cancel(color(black)(-$300))) * d)/cancel(color(red)(-$300))#
#2/30 = d#
#d = 2/30#
#d = 0.0bar6#
#d = (0bar6)/100#
"Percent" or "%" means "out of 100" or "per 100", Therefore #x/100# can be written as x%.
#d = bar6% = 6.bar6%#
The percent discount is approximately #6.7%#
