The ratio of the number of swans and red-crowned cranes in a nature reserve is 5:2. It is known that there are 105 red-crowned cranes and swans. How many swans are there?
一个自然保护区天鹅和丹顶鹤数量的比是5：2．已知丹顶鹤和天鹅共105只，天鹅有多少只．
<gadget id="calculator">5 + 2</gadget>
<output>7</output>

<gadget id="calculator">5 / 7</gadget>
<output>5/7 = around 0.714286</output>

<gadget id="calculator">105 * (5/7)</gadget>
<output>75</output>

<result>75</result>