If the area of the rectangle is 18, that means that the length and the width, when multiplied together, should equal 18.

$\displaystyle A=l\times w=18$

The only numbers from the answer choices that would result in the product of 18 are 9 by 2, which is therefore the correct answer. 

$\displaystyle l=9,\ w=2$

$\displaystyle 9\times2=18$

The area of a rectangle is the width times the length.

$\displaystyle A=w\times l$

The width is 4 feet and the length is 6 feet. Because 4 times 6 is 24, the area is 24 square feet. 

$\displaystyle A=4\text{ft}\times6\text{ft}$

$\displaystyle A=24\ \text{ft}^2$

The area of a rectangle is the width times the length.

$\displaystyle A=w\times l$

Given that the area is 20 square feet and the length is 5 feet, the width would have to be 4 feet because 5 times 4 is 20.

$\displaystyle 20\text{ft}^2=w\times5\text{ft}$

$\displaystyle w=\frac{20\text{ft}^2}{5\text{ft}}=4\text{ft}$

Given that the question asks for the width in inches, 4 should be multiplied by 12 (as there are 12 inches in a foot).

$\displaystyle 4\text{ft}\times12\text{inches per foot}=48\text{in}$

This gives us a product of 48 inches, which is the width. 

The area of a rectangle is found by multiplying the length by the width. Given that the length is 2r and that the length is 3w, the area will be the product of those numbers, which is $\displaystyle 6rw$.

The area of a rectangle is calculated by multiplying the length by the width.

$\displaystyle A=l\times w$

Given that the length is 10 feet and that the width is 1 foot we can multiply to find the final area:

$\displaystyle A=10\text{ft}\times1\text{ft}=10\text{ft}^2$

The area of a rectangle is equal to the length multiplied by the width. Since the width is 6 inches and the length is 7 inches, the area is equal to 6 times 7.

$\displaystyle A=l\times w$

$\displaystyle A=7\text{in}\times6\text{in}=42\text{in}^2$

The area is 42 square inches. 

The perimeter of a rectangle is equal to $\displaystyle width+width+length+length$. 

Thus, $\displaystyle 4+4+4x+4x=40$.

Add like terms:

$\displaystyle 8+8x=40$

Subtract 8 from both sides:

$\displaystyle 8x=32$

Divide both sides by 8:

$\displaystyle x=4$

If the rectangle has one side that is $\displaystyle 6$, we know that two of them must be that size. Therefore, we know that it looks something like this:

If the perimeter is 30, you know that the following equation holds:

$\displaystyle 12+2x = 30$

This means that the other two sides can be found by solving for $\displaystyle x$:

$\displaystyle 2x = 30-12$

$\displaystyle 2x = 18$

$\displaystyle \frac{2x}{2}=\frac{18}{2}$

$\displaystyle x=9$

The area of a rectangle is equal to its base times its height:

$\displaystyle A = 6*9=54$

If one side is $\displaystyle 10$, the doubled side must be $\displaystyle 20$. Therefore, the rectangle looks like this:

The area of a rectangle is equal to its base times its height:

$\displaystyle A = BH = 10 * 20 = 200$

The area of a rectangle is defined as the base multiplied by its height. Therefore, for this rectangle:

$\displaystyle A=12.4*8.3=102.92$