Answer: Well, there's not really a question here... but I can give you the value of each side. I'm assuming that is what the question is asking.
DE : 34 units
EF : 17 units
DF : 30 units
Step-by-step explanation:
You can start by making your equation. Let's say side EF is the value 'x'. Since DE is twice the value of EF, its value will be '2x'. Side DF is 4 units less than the length of side DE, which means that its value will be '2x - 4'
Now, all of these values added together will be 81, since that is the perimeter.
x + 2x + (2x-4) = 81
3x + (2x - 4) = 81
5x - 4 = 81
(Add four to both sides)
5x = 85
(Divide each side by 5)
x = 17
Now we know the value of x. All you have to do now is plug this in to find the lengths of each side. Since EF is just 'x', its length is 17.
DF is '2x', so its length it 2 times 17, or 34.
DE is '2x - 4', so its length will be 34 minus 4, or 30.
To check your answer, add all of these lengths together to make sure the add up to be 81, which is the perimeter.
17 + 34 + 30 = 81