There are a pile of coins with denominations of 1 cent, 2 cents and 5 cents. If the total denomination of the pile of coins is 1 yuan, the ratio of the number of coins with 2 cents to the number of coins with 1 cent is 2:13. So how many 5 cent coins are there?
有一堆硬币，硬币的面值为1分，2分，5分三种，如果这堆硬币面值的总和是1元，其中2分的硬币与1分的硬币的个数之比为2：13，那么5分硬币有多少枚．
<gadget id="calculator">10 * 2</gadget>
<output>20</output>

<gadget id="calculator">65 * 1</gadget>
<output>65</output>

<gadget id="calculator">100 - 20 - 65</gadget>
<output>15</output>

<gadget id="calculator">15 / 5</gadget>
<output>3</output>

<result>3</result>