Divide a large fish into three parts: head, body and tail. The tail of a fish weighs 4 kg. The mass of the head is equal to the mass of the tail plus half the mass of the body, and the mass of the body is equal to the mass of the head plus the mass of the tail. What is the mass of this fish in kilograms?
把一条大鱼分成鱼头、鱼身、鱼尾三部分．鱼尾重4千克，鱼头的质量等于鱼尾的质量加上鱼身一半的质量，而鱼身的质量等于鱼头的质量加上鱼尾的质量．这条大鱼的质量是多少千克．
<gadget id="calculator">4 + 4</gadget>
<output>8</output>

<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">1 - (1/2)</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">8 / (1/2) / 2</gadget>
<output>8</output>

<gadget id="calculator">8 / (1/2)</gadget>
<output>16</output>

<gadget id="calculator">8 + 4 + 16 + 4</gadget>
<output>32</output>

<result>32</result>