Question 914468
y, the costlier fertilizer, number of bags
x, the number of bags of cheaper fertilizer
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Observe that the question is how many bags, but not how many pounds.


The mixture to result must be {{{28/1}}} dollars per bag.
{{{(46*y+8*x)/(x+y)=28}}}


Accounting for count of bags, {{{x+y=19}}}.


The "50-pound bag" part of the description is just an informative distraction to solving the problem.  This problem is the same general type as discussed and solved in the lesson:   <a href="http://www.algebra.com/my/mixture-price-two-part-both-parts-unknown.lesson?content_action=show_dev">http://www.algebra.com/my/mixture-price-two-part-both-parts-unknown.lesson?content_action=show_dev</a>,  but now that you can plainly see the needed equations for this question, you can simply solve the system for x and y.