If 3 play all three sports, and 10 play both football and soccer, the 7 (10 minus the 3 that do all three) play ONLY F and S. Likewise, 5 play both S and B, so 5 minus 3 = 2 play ONLY S and B. And then 9 minus 3 is 6 play only F and B. The 7 that play ONLY F and S, the 3 that play all three, and the 6 that play only F and B add up to 16 that play F and something else, so 19 minus 16 leaves 3 that play F ONLY. Likewise, 5 play S ONLY. Summary:
F only 3 S only 5 F and S only 7 F and B only 6 S and B only 2 All three 3
These add up to 26. Since all 30 boys did something...
You can figure the rest.
John
My calculator said it, I believe it, that settles it
