There are four boxes of black and white balls, each box contains 60 balls, the first box contains the same number of white balls as the second box contains black balls, the third box contains all white balls, and the fourth box contains 25% white balls. How many white balls are there in all four boxes?
有四盒黑白皮球，每盒60个，第一盒里白皮球和第二盒里的黑皮球个数同样多，第三盒里全是白皮球，第四盒里的25%是白皮球．这四个盒子里一共有多少个白皮球？
<gadget id="calculator">25 / 100</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">60 * (1/4)</gadget>
<output>15</output>

<gadget id="calculator">60 + 60 + 15</gadget>
<output>135</output>

<result>135</result>