>597
取り出し方は
10Ｃ3=120(通り)

①和が10
(9,1,0)(8,2,0)(7,3,0)(7,2,1)(6,4,0)(6,3,1)(5,4,1)(5,3,2) 8通り
②和が12
(9,3,0)(9,2,1)(8,4,0)(8,3,1)(7,5,0)(7,4,1)(7,3,2)(6,5,1)(6,4,2)(5,4,3) 10通り
③和が14
(9,5,0)(9,4,1)(9,3,2)(8,6,0)(8,5,1)(8,4,2)(7,6,1)(7,5,2)(7,4,3)(6,5,3) 10通り
④和が16
(9,7,0)(9,6,1)(9,5,2)(9,4,3)(8,7,1)(8,6,2)(8,5,3)(7,6,3)(7,5,4) 9通り
⑤和が18
(9,8,1)(9,7,2)(9,6,3)(9,5,4)(8,7,3)(8,6,4)(7,6,5) 7通り
⑥和が20
(9,8,3)(9,7,4)(9,6,5)(8,7,5) 4通り
⑦和が22
(9,8,5)(9,7,6) 2通り
⑧和が24
(9,8,7) 1通り

8+10+10+9+7+4+2+1=51
よって
51/120 = 17/40