The number A is 7/9 of the number B. The sum of the two numbers is 80. What is the number A?
甲数是乙数的九分之七，甲乙两数的和是80，甲数是多少．
<gadget id="calculator">7 + 9</gadget>
<output>16</output>

<gadget id="calculator">7 / 16</gadget>
<output>7/16 = around 0.4375</output>

<gadget id="calculator">80 * (7/16)</gadget>
<output>35</output>

<result>35</result>