4 people, A, B, C, and D, have a total of 900 stamps. If A’s stamps are added to 20, B’s is subtracted from 20, C’s is multiplied by 2, and D’s is divided by 2, then the number of stamps of the 4 people is exactly equal. Q: How many stamps does A have?
甲乙丙丁4人一共有900枚邮票，若把甲的邮票加20枚，乙的减20枚，丙的乘以2，丁的除以2，则4人的邮票数正好相等．问：甲有多少枚邮票？
<gadget id="calculator">900 - 20</gadget>
<output>880</output>

<gadget id="calculator">20 + 880</gadget>
<output>900</output>

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

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

<gadget id="calculator">900 / (9/2)</gadget>
<output>200</output>

<gadget id="calculator">200 - 20</gadget>
<output>180</output>

<result>180</result>