Answer: 30% or $ 135.
Step-by-step explanation
The mark up is generally expressed as a percentage. It is the percent increase on the cost.
We can calculate the mark up from cost to sale price of the item as a composition of steps. That is what the next steps show.
1) First step: calculate the the price after the item is marked down by 10%:
Selling price: $ 650
Mark down = 10% of 650 = 0.10 × $ 650 = $65
Price after mark down: $ 650 - $ 65 = $ 585.
2) Second step: difference of the price marked down to the cost:
$ 585 - $ 450 = $ 135
3) Calculate the percent mark up:
% mark up = (mark up / cost) × 100 = ($ 135 / $ 450) × 100 = 30%