15 yellow and white balls of the same size are placed in a box. Randomly touch a ball, so that the possibility of touching a white ball is (3/5), how many yellow balls should be placed.
往盒子里放15个同样大小的黄、白两种颜色的球．任意摸一个球，要使摸到白球的可能性是(3/5)，黄球应放多少个．
<gadget id="calculator">3 / 5</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">15 * (3/5)</gadget>
<output>9</output>

<gadget id="calculator">15 - 9</gadget>
<output>6</output>

<result>6</result>