The sum of the two numbers A and B is 300, the ratio of the two numbers A and B is 5:7, what is the number A
甲、乙两个数的和是300，甲、乙两数的比是5：7，甲数是多少
<gadget id="calculator">5 + 7</gadget>
<output>12</output>

<gadget id="calculator">300 / 12</gadget>
<output>25</output>

<gadget id="calculator">25 * 5</gadget>
<output>125</output>

<result>125</result>