Answer: 21 basketball players, 9 girl basketball players, and 12 boy basketball players.
Step-by-step explanation: 630 divided by 15 is 42, multipled by 2 is 84 sport players. 1/4 of 84 is 21 basketball players. 3/7 of 21 is 9 girl basketball players. 21 - 9 is 12 boy basketball players.