Question 1037123
<i>A candy store sells 8 pound bags of mixed almonds and cashews. If c pounds of cashews are in a bag,...</i>


c=1 was already given as described.  The store sells pound bags.


The rest of the description and question seem not to match.  Maybe each bag contains 8 pounds of the two nuts.  Eight pounds and some of this is of cashews.  Now, c is how many pounds of cashews in one bag.
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{{{p=2.59*c+1.72(8-c)}}}
You want to know the quantity of cashews if p=18.11 dollars per bag.
{{{2.59c+1.72*8-1.72c=p}}}
{{{2.59c-1.72c=p-1.72*8}}}
{{{(2.59-1.72)c=p-1.72*8}}}
{{{0.87c=p-13.76}}}
{{{highlight_green(c=(p-13.76)/0.87)}}}-------plug in p=18.11.