The length of a rectangle is $3x+10$ feet and its width is $x+12$ feet.  If the perimeter of the rectangle is 76 feet, how many square feet are in the area of the rectangle?
<|im_start|>system
You are a helpful assistant.<|im_end|>
<|im_start|>user
The length of a rectangle is $3x+10$ feet and its width is $x+12$ feet.  If the perimeter of the rectangle is 76 feet, how many square feet are in the area of the rectangle?
Please reason step by step, and put your final answer within \boxed{{}}.<|im_end|>
<|im_start|>assistant

user
352
The length of a rectangle is $3x+10$ feet and its width is $x+12$ feet.  If the perimeter of the rectangle is 76 feet, how many square feet are in the area of the rectangle?
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