Draw a picture first, and you can see that the teacher is much younger than Xiao Gan ten years ago and twice as big as Xiao Gan ten years ago. This is the age difference that will not change.

14 years later, both the teacher and Xiao gan will grow up, 24 years older than 10 years ago. If their age difference is 2n, then 0.4 of n+24 is equal to the age difference, so we can know that the age difference is 0.8 times =24×0.4, and we can calculate that the age difference is 12 years old. So ten years ago, Xiao Gan's age was 12÷2=6, so Xiao Gan's age was 10+6= 16, and the teacher's age was (12+6)+/kloc-0 = 28 (years old