(ただし1と2を合せて12のような使い方は出来ません。)
37個の解法が見つかりました。
((2+(7+9))-8)=10
((2+7)+(9-8))=10
((2+7)-(8-9))=10
((2+9)+(7-8))=10
((2+9)-(8-7))=10
((2-8)+(7+9))=10
((7+(2+9))-8)=10
((7+9)+(2-8))=10
((7+9)-(8-2))=10
((7-8)+(2+9))=10
((9+(2+7))-8)=10
((9-8)+(2+7))=10
(2+((7+9)-8))=10
(2+(7+(9-8)))=10
(2+(7-(8-9)))=10
(2+(9+(7-8)))=10
(2+(9-(8-7)))=10
(2-((8-7)-9))=10
(2-((8-9)-7))=10
(2-(8-(7+9)))=10
(7+((2+9)-8))=10
(7+(2+(9-8)))=10
(7+(2-(8-9)))=10
(7+(9+(2-8)))=10
(7+(9-(8-2)))=10
(7-((8-2)-9))=10
(7-((8-9)-2))=10
(7-(8-(2+9)))=10
(9+((2+7)-8))=10
(9+(2+(7-8)))=10
(9+(2-(8-7)))=10
(9+(7+(2-8)))=10
(9+(7-(8-2)))=10
(9-((8-2)-7))=10
(9-((8-7)-2))=10
(9-(8-(2+7)))=10