Divide a large fish into three parts: head, body and tail. The tail weighs 5 kg. The weight of the head is equal to half the weight of the body, and the weight of the body is equal to the weight of the head plus three tails. How many kilograms does this big fish weigh?
把一条大鱼分成鱼头、鱼身和鱼尾三部分，鱼尾重5千克，鱼头的重量等于鱼身的重量的一半，而鱼身的重量等于鱼头的重量加上三个鱼尾的重量，这条大鱼的重多少千克？
<gadget id="calculator">10 * 5</gadget>
<output>50</output>

<result>50</result>