There are three numbers, A:C=4:3, C:B=5:3, the sum of A and B is 87, what is the difference between B and C?
有三个数，甲：丙=4：3，丙：乙=5：3，甲、乙两数的和是87，则乙、丙两数的差是多少．
<gadget id="calculator">20 + 9</gadget>
<output>29</output>

<gadget id="calculator">87 / 29</gadget>
<output>3</output>

<gadget id="calculator">3 * 5 * 3</gadget>
<output>45</output>

<gadget id="calculator">9 * 3</gadget>
<output>27</output>

<gadget id="calculator">45 - 27</gadget>
<output>18</output>

<result>18</result>