A, B and C produce parts, the ratio of the number of people in factory A to the number of people in factory B is 2:3, the number of people in factory B is 4:5 to the number of people in factory C, it is known that the number of people in factory C is 15 fewer than the sum of the number of people in factories A and B ． Question: How many workers are there in Factory A, B, and C?
甲、乙、丙生产零件，甲厂人数与乙厂人数比为2：3，乙厂人数比丙厂人数为4：5，已知丙厂人数比甲、乙两厂人数的总和少15人．问：甲、乙、丙三个厂共有多少人？
<gadget id="calculator">12 - 15</gadget>
<output>-3</output>

<gadget id="calculator">8 + (-3)</gadget>
<output>5</output>

<gadget id="calculator">15 / 5</gadget>
<output>3</output>

<gadget id="calculator">8 + 12 + 15</gadget>
<output>35</output>

<gadget id="calculator">3 * 35</gadget>
<output>105</output>

<result>105</result>