There are 20 basketballs in the store, the number of footballs is 2 fewer than basketballs, and the number of volleyballs is 6 fewer than twice as many footballs. How many volleyballs are there in the store?
商店里有20个篮球，足球的个数比篮球少2个，排球的个数比足球的2倍少6个．商店里有排球多少个？
<gadget id="calculator">20 - 2</gadget>
<output>18</output>

<gadget id="calculator">18 * 2</gadget>
<output>36</output>

<gadget id="calculator">36 - 6</gadget>
<output>30</output>

<result>30</result>