Answer:
perimeter = x + y + 14
Explanation:
The perimeter is the sum of the side lengths:
perimeter = x + 7 + y + 7
The constants can be combined to give ...
perimeter = x + y + 14
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An "equation" will have an equal sign somewhere. Since you want to find the perimeter, it makes sense for the equation to show you how to find the perimeter. (I have used "perimeter" to represent the perimeter. It is often represented using the letter P. Of course, you can choose any variable or other representation you like.)