Answer:

Step-by-step explanation:
Given,
Length of a rectangle = 20 inches
Perimeter of a rectangle = 64 inches
Area of a rectangle = ?
Let width of a rectangle be ' w ' .
<u>Fi</u><u>rst</u><u>,</u><u> </u><u>finding </u><u>the</u><u> </u><u>width</u><u> </u><u>of</u><u> </u><u>a</u><u> </u><u>rectangle</u>

plug the values
⇒
Distribute 2 through the parentheses
⇒
Swap the sides of the equation
⇒
Move 2w to right hand side and change it's sign
⇒
Subtract 40 from 64
⇒
Divide both sides of the equation by 2
⇒
Calculate
⇒
Width of a rectangle ( w ) = 12 inches
<u>Now</u><u>,</u><u> </u><u>finding</u><u> </u><u>the</u><u> </u><u>area</u><u> </u><u>of </u><u>a</u><u> </u><u>rectangle</u><u> </u><u>having</u><u> </u><u>length</u><u> </u><u>of</u><u> </u><u>2</u><u>0</u><u> </u><u>inches</u><u> </u><u>and </u><u>width </u><u>of</u><u> </u><u>1</u><u>2</u><u> </u><u>inches</u>

plug the values
⇒
Multiply the numbers : 20 and 12
⇒
Hence, Area of a rectangle = 240 inches²
Hope I helped !
Best regards!