Answer:
a) See attachment.

c) 125%
Explanation:
Part (a)
Let x be the width of the original square garden.
If a new garden has the same width as the original garden, then the width of the new garden is also x.
If the new garden has a length that is 3 feet more than twice the width of the original garden, then the length of the new garden is 2x + 3.
Part (b)
The area of a square is the square of its side length.
As the original garden is a square with side length x, the equation for its area is:

The area of a rectangle is the product of its width and length.
As the area of the new garden is a rectangle with w = x and l = 2x + 3, the equation for its area is:

The formula for percentage increase is:

The initial value is the area of the original garden, and the final value is the area of the new garden. Therefore:

Part (c)
To determine the percent of increase in area if the original garden was a 12-foot square, substitute x = 12 into the expression found in part (b):

Therefore, the percent of increase in area is 125%.
To check the answer, calculate the area of the original garden by squaring the side length of 12 feet:

Calculate the area of the new garden by multiplying the width (12 feet) by the length (3 feet more than twice the width = 27 feet):

The increase in area between the old garden and the new garden is the difference between the two areas:

To find the percentage increase, divide the difference by the area of the original garden and multiply by 100:

Therefore, this confirms that the percent of increase in area is 125%.