There are 15 volleyballs in the sports room of a certain school. The number of footballs is 4 times that of volleyballs. How many more footballs are there than volleyballs?
某校体育室里有15个排球，足球的个数是排球的4倍，足球的个数比排球多多少个？
<gadget id="calculator">15 * 4</gadget>
<output>60</output>

<gadget id="calculator">60 - 15</gadget>
<output>45</output>

<result>45</result>