A ship sails from port A to port B along the current. When sailing from port B to port A, it travels against the current. It is known that the speed of the ship traveling along the current and against the current is 4:3, and it takes 12 hours for a round trip. , find the time taken from port A to port B.
一艘轮船从A港开往B港是顺水而行，从B港开往A港时，逆水而行，已知轮船顺水而行与逆水而行的速度是4：3，往返一次共用12小时，求从A港到B港所用的时间．
<gadget id="calculator">4 + 3</gadget>
<output>7</output>

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

<gadget id="calculator">12 * (3/7)</gadget>
<output>36/7 = around 5.142857</output>

<result>36/7 = around 5.142857</result>