There is a pile of black and white pieces, black pieces are twice as many as white pieces, first take out 4 black pieces each time, and 3 white pieces, after several times, the white pieces are taken out and the remaining 16 pieces are left, ask how many pieces there are in this pile.
有黑白一堆棋子，黑子是白子的两倍，先每次取出黑子4个，白子3个，若干次后白子取完黑子剩余16个，问这堆棋子原共有多少个．
<gadget id="calculator">3 * 2</gadget>
<output>6</output>

<gadget id="calculator">6 - 4</gadget>
<output>2</output>

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

<gadget id="calculator">8 * 3</gadget>
<output>24</output>

<gadget id="calculator">1 + 2</gadget>
<output>3</output>

<gadget id="calculator">24 * 3</gadget>
<output>72</output>

<result>72</result>