PLEASE READ:

We apologize for the little error made in the video.

0:46 You will notice that the rate given in the problem is 20% while..
1:46 the rate given was suddenly changed to 15%

Even if the rate given was changed, the process in getting mark up price is the same, and the answer is still correct given the 15% as the rate. (Please disregard the first given which is 20% as the rate, to avoid confusion).

Thank you!