一道英语数学题（也可以说就是一道数学题）
At the end of 2005 Walter was half as old as his grandmother.The sum of the years which they were born in is 3860.How old would Walter be the end of 2006?
在2005年时walter的年龄是他外婆年龄的一半,两个人的出生日期加起来是3860.那么在2006年walter的年龄是多少?
这道题的英语和汉语我都有!甚至连答案都有（可能是51岁我不知道对不对）,可我有些不明白!望大哥大姐帮忙做一下可以讲解一下更好!好的加分!
急需快点我在线等!