If the multiplicand increases by 15, the multiplier remains unchanged and the product increases by 180. If the multiplicand remains unchanged and the multiplier increases by 4, then the product increases by 120. What is the product of the original two numbers?
如果被乘数增加15，乘数不变、积就增加180．如果被乘数不变，乘数增加4，那么积就增加120，原来两个数相乘的积是多少．
<gadget id="calculator">120 / 4</gadget>
<output>30</output>

<gadget id="calculator">180 / 15</gadget>
<output>12</output>

<gadget id="calculator">30 * 12</gadget>
<output>360</output>

<result>360</result>