The cost to purchase enough of a certain fertilizer to treat a garden is $.25 per square foot of the garden, plus $20.00 for shipping. Write an equation describing the cost in dollars to purchase fertilizer for a garden that is 12 feet longer than it is wide. Use x to represent the width of the garden.

For this case we have the following variable:

x: represent the width of the garden

So, the length of the garden is:

l = x + 12

The garden area is:

A = (x) * (x + 12)

Then, the cost equation is:

C = 0.25A + 20

Rewriting:

C = 0.25 * (x) * (x + 12) + 20

Answer:

An equation describing the cost in dollars to purchase fertilizer is:

C = 0.25 * (x) * (x + 12) + 20