Grandpa's age this year is 6 times that of Xiaoming's. After a few years, grandpa's age will be 5 times that of Xiaoming's. A few years later, grandpa's age is four times that of Xiaoming's. Ask grandpa what is his age this year?
爷爷今年的年龄是小明年龄的6倍，几年后，爷爷年龄是小明年龄的5倍．又过几年后，爷爷的年龄是小明年龄的4倍，问爷爷今年的年龄是多少？
<result>72</result>