A batch of pencils is distributed to A, B, and C, one-seventh is distributed to A, and one-fourth is distributed to B. The amount distributed to C is twice the difference between the amounts distributed to A and B. At this time There are 22 pencils left, how many pencils does A get.
一批铅笔分给甲、乙、丙三人，分给甲七分之一，分给乙四分之一，分给丙的数量是分给甲、乙二人数量差的2倍，这时还剩下22支铅笔，甲分到多少支铅笔．
<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">1 / 7</gadget>
<output>1/7 = around 0.142857</output>

<gadget id="calculator">1 - (1/4) - (1/7)</gadget>
<output>17/28 = around 0.607143</output>

<gadget id="calculator">(1/4) - (1/7)</gadget>
<output>3/28 = around 0.107143</output>

<gadget id="calculator">(3/28) * 2</gadget>
<output>3/14 = around 0.214286</output>

<gadget id="calculator">(17/28) - (3/14)</gadget>
<output>11/28 = around 0.392857</output>

<gadget id="calculator">22 / (11/28)</gadget>
<output>56</output>

<gadget id="calculator">56 * (1/7)</gadget>
<output>8</output>

<result>8</result>