A, B, and C go to buy books. B buys 3 more books than A (3/7), and C buys 1 less than A (2/5). So, how many books did the three of them buy together at least?
甲、乙、丙三人去买书，乙买的书比甲买的书的本数的(3/7)多3本，丙买的书比甲买的书的(2/5)少1本．那么，三人合计最少买了多少本书．
<gadget id="calculator">3 / 7</gadget>
<output>3/7 = around 0.428571</output>

<gadget id="calculator">35 * (3/7)</gadget>
<output>15</output>

<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">35 * (2/5)</gadget>
<output>14</output>

<gadget id="calculator">14 - 1</gadget>
<output>13</output>

<gadget id="calculator">35 + 15 + 3 + 13</gadget>
<output>66</output>

<result>66</result>