Question 992018
Same idea but using PRICE instead of PERCENT:
<a href="https://www.youtube.com/watch?v=-REjxT9KCzQ">This is how it works, a video example, but question is the same form.</a>


If you want a more general lesson  but in two unknown variables instead of just one, <a href="http://www.algebra.com/my/mixture-price-two-part-both-parts-unknown.lesson?content_action=show_dev">two part mixture, price, lesson</a>