There are 5 black balls, 10 red balls, and several white balls of the same size and shape in a box. If you touch a ball randomly, how many white balls should be placed in the box in order to make the probability of touching a white ball be (3/8).
盒子里有大小形状都相同的黑球5个、红球10个、白球若干．任意摸一个球，要想使摸到白球的可能性是(3/8)，盒子里应放多少个白球．
<gadget id="calculator">5 + 10</gadget>
<output>15</output>

<gadget id="calculator">3 / 8</gadget>
<output>3/8 = around 0.375</output>

<gadget id="calculator">1 - (3/8)</gadget>
<output>5/8 = around 0.625</output>

<gadget id="calculator">15 / (5/8)</gadget>
<output>24</output>

<gadget id="calculator">24 - 15</gadget>
<output>9</output>

<result>9</result>