A video game sells at Arnolds for $14.99. Arnolds marks the game up at 40% of the selling price. The cost of the video game to Arnold is:

If they increase 40% the answer would be $20.99, if they make a discount of 40% the answer would be $8.99. You just find 10% of 14.99 which is 1.5, you move the decimal to the left once and you round your answer. Then you multiply 1.5 times 4 = 6. Then you add that to 14.99 if 40% is increasing or you subtract it if there is a discount of 40%.