（1）25 (2)20(3)9过程(1) (1,10);(2,9;)(2,10 );(3,8);(3,9);(3,10 ) (4,7) (4,8) (4,9) (4,10)(5,6)(5,7) (5,8) (5,9)
(5,10) (6,7)(6,8) (6,9)(6,10)(7,8) (7,9)(7,10)(8,9) (8,10)(9,10)
(2) (2,10) (3,9)(3,10)(4,8)(4,9)(4,10) (5,7)(5,8)(5,9)(5,10)(6,7) (6,8)(6,9)(6,10)(7,8)(7,9)
(7,10)(8,9)(8,10)(9,10)
(3) (3,8)(4,7)(4,8) (5,6)(5,7)(5,8)(6,7)(6,8)(7,8) 括号中的一组数是一种取法