A certain circle's area is $x$ square units, and its circumference is $y$ units. The value of $x + y$ is $80\pi$. What is the radius of the circle, in units?
Question:
A certain circle's area is $x$ square units, and its circumference is $y$ units. The value of $x + y$ is $80\pi$. What is the radius of the circle, in units?
Answer:
Let's think step by step.

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A certain circle's area is $x$ square units, and its circumference is $y$ units. The value of $x + y$ is $80\pi$. What is the radius of the circle, in units?
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