First take 36% off of the original price, then take an additional 11% off of the discounted price:
1788.13 - 0.36(1788.13) = 1144.40
1144.30 - 0.11(1144.40) = 1018.52
London Drugs sale price = $1018.52
Future Shop sale price = 1785.71 - 0.22(1785.71)
= 1785.71(1 - 0.22)
= 1785.71(0.78)
= $1392.85
$1392.85 - $1018.52 = $374.33
Future Shop should offer an additional discount of $374.33 to match the price of London Drugs.