Four children jointly buy a 180 yuan boat, the first child pays half of the total amount paid by other children, and the second child pays (1/3) the total amount paid by other children , the third child pays (1/4) the total amount of other children's money. How much did the fourth child pay?
四个孩子合买一只180元的小船，第一个孩子付的钱是其他孩子付的总钱数的一半，第二个孩子付的钱是其他孩子的总钱数的(1/3)，第三个孩子付的钱是其他孩子的总钱数的(1/4)．第四个孩子付了多少元？
<gadget id="calculator">1 + 2</gadget>
<output>3</output>

<gadget id="calculator">1 / 3</gadget>
<output>1/3 = around 0.333333</output>

<gadget id="calculator">1 + 3</gadget>
<output>4</output>

<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">1 + 4</gadget>
<output>5</output>

<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">(1/3) + (1/4) + (1/5)</gadget>
<output>47/60 = around 0.783333</output>

<gadget id="calculator">1 - (47/60)</gadget>
<output>13/60 = around 0.216667</output>

<gadget id="calculator">180 * (13/60)</gadget>
<output>39</output>

<result>39</result>