The product of the average of the two numbers A and B and the number C is 270. Given that the number A is 20 and the number C is 9, what is the number B?
甲、乙两个数的平均数与丙数的积是270，已知甲数是20，丙数是9，乙数是多少？
<gadget id="calculator">20 / 2</gadget>
<output>10</output>

<gadget id="calculator">10 * 9</gadget>
<output>90</output>

<gadget id="calculator">270 - 90</gadget>
<output>180</output>

<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">(1/2) * 9</gadget>
<output>9/2 = around 4.5</output>

<gadget id="calculator">180 / (9/2)</gadget>
<output>40</output>

<result>40</result>