In an Aurangabad club, 30 members play chess. After finding the number marked ?, how many members play exactly one of the three games?

The Chess circle: $?+5+6+3=30$, so $?=16$. Exactly one $=12+16+19=47$. 31 leaves out the ?, 50 comes from forgetting the centre 3 when finding ?, and 61 uses the whole Chess circle (30) instead of chess only.