Let the track set be A, the field set be B, the ball set be C, the number of people who only participate in A is A, the number of people who only participate in B is B, the number of people who only participate in C is C, and then let the number of people who participate in A and C at the same time be X, and then the following equation can be drawn from the meaning of the question:

a+2+x= 15

2+ 1+2+b=8

c+x+2= 14

a+b+c+4+x=27

Combining the above equations, we can get:

a=8

b=3

c=7

x=5

Therefore, the number of participants in both track and field and ball games is 5, and the number of participants in only one game is a+b+c= 18.