The sum of the numbers A and B is 320, the number B is three times the number A, what is the number A?
甲乙两数的和是320，乙数是甲数的3倍，甲数是多少．
<gadget id="calculator">3 + 1</gadget>
<output>4</output>

<gadget id="calculator">320 / 4</gadget>
<output>80</output>

<result>80</result>