Cod is $4 per pound and salmon is $7 per pound?

Question

The owner of Pagel’s Fish Market orders cod and salmon. He wants to buy at least 50 pounds of fish but cannot spend more than $300.

Answer 1

Let C be the pounds of cod and S be the pounds of salmon.  Then cost is:

 

4C + 7S

 

So, the limitations can be expressed as:

 

4C + 7S ≤ 300

C + S ≥ 50

 

This set of inequalities defines the solution set.  If that doesn't answer your question, please let me know.