(ただし1と2を合せて12のような使い方は出来ません。)
38個の解法が見つかりました。
((4+7)+(8-9))=10
((4+7)-(9-8))=10
((4+8)+(7-9))=10
((4+8)-(9-7))=10
((4-9)+(7+8))=10
((7+(4+8))-9)=10
((7+8)+(4-9))=10
((7+8)-(9-4))=10
((7-9)+(4+8))=10
((8+(4+7))-9)=10
((8-9)+(4+7))=10
(4+((7+8)-9))=10
(4+(7+(8-9)))=10
(4+(7-(9-8)))=10
(4+(8+(7-9)))=10
(4+(8-(9-7)))=10
(4-((9-7)-8))=10
(4-((9-8)-7))=10
(4-(9-(7+8)))=10
(7+((4+8)-9))=10
(7+(4+(8-9)))=10
(7+(4-(9-8)))=10
(7+(8+(4-9)))=10
(7+(8-(9-4)))=10
(7-((9-4)-8))=10
(7-((9-8)-4))=10
(7-(9-(4+8)))=10
(8+((4+7)-9))=10
(8+(4+(7-9)))=10
(8+(4-(9-7)))=10
(8+(4÷(9-7)))=10
(8+(7+(4-9)))=10
(8+(7-(9-4)))=10
(8-((9-4)-7))=10
(8-((9-7)-4))=10
(8-(4÷(7-9)))=10
(8-(9-(4+7)))=10