Question 877984
See this lesson and study it.
<a href="http://www.algebra.com/tutors/Two-Part-Mixture-with-one-material-quantity-unknown.lesson?content_action=show_dev">This includes how to solve.  http://www.algebra.com/tutors/Two-Part-Mixture-with-one-material-quantity-unknown.lesson?content_action=show_dev</a>