The sum of the three numbers is 120, the number A is twice the number B, and C is 20 more than B, what is the number A?
三数之和是120，甲数是乙数的2倍，丙比乙多20，甲数是多少．
<gadget id="calculator">120 - 20</gadget>
<output>100</output>

<gadget id="calculator">1 + 2 + 1</gadget>
<output>4</output>

<gadget id="calculator">100 / 4</gadget>
<output>25</output>

<gadget id="calculator">25 * 2</gadget>
<output>50</output>

<result>50</result>