First of all, you should know that seven years later, Dad is still 28 years older than Liang Xiao, and he will grow with you. Secondly, seven years later, the father's age is just three times that of Xiao Liang, which can be understood as the father's age is 3- 1=2 times older than that of his son. This is much simpler.

Seven years later, my son's age is

28/2= 14 years old

My son's age this year is

14-7=7 years old

Dad's age this year is?

7+28=35 years old or 14*3-7=35 years old.