The school has two track and field teams, A and B. The ratio of the number of A and B teams is 4:3. If 5 people are transferred from A to B, the ratio of A and B is 3:4. How many people are there in B?
学校有甲乙两个田径队，甲乙两队人数之比是4：3，如果从甲队调5人到乙队，则甲乙两队的比是3：4，乙队原有多少人？
<gadget id="calculator">4 + 3</gadget>
<output>7</output>

<gadget id="calculator">4 / 7</gadget>
<output>4/7 = around 0.571429</output>

<gadget id="calculator">3 / 7</gadget>
<output>3/7 = around 0.428571</output>

<gadget id="calculator">(4/7) - (3/7)</gadget>
<output>1/7 = around 0.142857</output>

<gadget id="calculator">5 / (1/7)</gadget>
<output>35</output>

<gadget id="calculator">35 * (3/7)</gadget>
<output>15</output>

<result>15</result>