(ただし1と2を合せて12のような使い方は出来ません。)
44個の解法が見つかりました。
((1+(9+9))-9)=10
((1+9)×(9÷9))=10
((1+9)+(9-9))=10
((1+9)-(9-9))=10
((1+9)÷(9÷9))=10
((1-9)+(9+9))=10
((9×(1+9))÷9)=10
((9+(1+9))-9)=10
((9+(9÷9))÷1)=10
((9+9)+(1-9))=10
((9+9)-(9-1))=10
((9-9)+(1+9))=10
((9÷1)+(9÷9))=10
((9÷9)×(1+9))=10
((9÷9)+(1×9))=10
((9÷9)+(9÷1))=10
(1×(9+(9÷9)))=10
(1+((9×9)÷9))=10
(1+((9+9)-9))=10
(1+(9×(9÷9)))=10
(1+(9+(9-9)))=10
(1+(9-(9-9)))=10
(1+(9÷(9÷9)))=10
(1-((9-9)-9))=10
(1-(9-(9+9)))=10
(9×((1+9)÷9))=10
(9+((1×9)÷9))=10
(9+((1+9)-9))=10
(9+((9÷1)÷9))=10
(9+((9÷9)÷1))=10
(9+(1×(9÷9)))=10
(9+(1+(9-9)))=10
(9+(1-(9-9)))=10
(9+(1÷(9÷9)))=10
(9+(9×(1÷9)))=10
(9+(9+(1-9)))=10
(9+(9-(9-1)))=10
(9+(9÷(1×9)))=10
(9+(9÷(9÷1)))=10
(9-((9-1)-9))=10
(9-((9-9)-1))=10
(9-(9-(1+9)))=10
(9÷(9÷(1+9)))=10