求救~~PREP一道数学题！！

honeyxin

honeyxin

截来截去，下面的条件始终看不清，郁闷~~还是自己打出来吧~~
The table shows the number of shares of each of the 5 stocks owned by Mr.Sami.If Mr. Sami was to sell 20 shares of Stock X and buy 24 shares of Stock Y,what would be the increase in the range of the numbers of shares of the 5 stocks owned by Mr. Sami?选项分别是4，6，9，15，20.
拜托XDJM帮忙解答一下吧~！谢谢了~~！