There are 5 yuan, 10 yuan, and 20 yuan banknotes in Mingming's lucky money, a total of 525 yuan. The number of the three kinds of banknotes is the same. How many pieces of each banknote are there in his lucky money.
明明的压岁钱中有5元、10元、20元的纸币共525元，三种纸币的张数相同，他的压岁钱中每种纸币有多少张．
<gadget id="calculator">5 + 10 + 20</gadget>
<output>35</output>

<gadget id="calculator">525 / 35</gadget>
<output>15</output>

<result>15</result>