Suppose Xiao Ming's age is X this year, and his father's age is five times that of Xiao Ming. It is understood that his father's age is 5X that of three years ago, and his father's age is eight times that of Xiao Ming. The equation can be listed as: 5*X-3=8*(X-3) and X=7, so this year his father's age is 35 and Xiaoming's age is 7.

The formula is as follows:

5*X-3=8*(X-3)

5 X 3 = 8 X 8 X 3

5 X 3 = 8 X 24

24-3 = 8 X-5 X

3*X=2 1

X=7