Xiaoming has 50 stamps, Xiaoqiang has 30 stamps, Xiaoqiang wants to collect as many stamps as Xiaoming, Xiaoming collects 5 stamps every month, Xiaoqiang collects 9 stamps every month. How many months will it take for the two to collect the same amount of stamps?
小明有邮票50枚，小强有邮票30枚，小强想和小明集同样多的邮票，小明每月集邮票5枚，小强每月集邮票9枚．几个月后两人集的邮票才一样多？
<gadget id="calculator">50 - 30</gadget>
<output>20</output>

<gadget id="calculator">9 - 5</gadget>
<output>4</output>

<gadget id="calculator">20 / 4</gadget>
<output>5</output>

<result>5</result>