Question

how many play kabaddi only.

Answer 1

Let A, B, and C be the sets of players forming kabaddi, kho-kho, and football teams, respectively. Then
$n\left(A\right)=21$, $n\left(B\right)=26$, $n\left(C\right)=29$, $n(A\cap B)=14$,
$n(A\cap C)=12$, $n(B\cap C)=15$ and $n(A\cap B\cap C)=8$.
From the diagram
The number of kabaddi players (only kabaddi) is $=21-(6+8+4)=3$