x and y are the packs of organic and inorganic fertilizer, respectively.
pounds of nitrogen added = 2x + 6y = 120
pounds of potassium added = 3x + 2y = 54
eliminate the y terms. subtract the first equation from 3 times the second equation.
9x + 6y = 162
-2x - 6y = -120
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7x = 42
x = 6
y = 18
Answer:

Step-by-step explanation:
Expression for the rectangular area and perimeter are, respectively:


After some algebraic manipulation, area expression can be reduce to an one-variable form:


The first derivative of the previous equation is:

Let the expression be equalized to zero:


The second derivative is:

According to the Second Derivative Test, the critical value found in previous steps is a maximum. Then:

The maximum area is:


Step-by-step explanation:
Jose bought 750 bags for $375.00
Each bag cost $375/750= $0.50
He intends to sells them for $0.15 more
He should charge : $0.5 +$0.15=$0.65