(ただし1と2を合せて12のような使い方は出来ません。)
21個の解法が見つかりました。
((4+4)+(9-7))=10
((4+4)-(7-9))=10
((4+9)+(4-7))=10
((4+9)-(7-4))=10
((4-7)+(4+9))=10
((9+(4+4))-7)=10
((9-7)+(4+4))=10
(4+((4+9)-7))=10
(4+(4+(9-7)))=10
(4+(4-(7-9)))=10
(4+(9+(4-7)))=10
(4+(9-(7-4)))=10
(4-((7-4)-9))=10
(4-((7-9)-4))=10
(4-(7-(4+9)))=10
(9+((4+4)-7))=10
(9+(4+(4-7)))=10
(9+(4-(7-4)))=10
(9-((7-4)-4))=10
(9-(7-(4+4)))=10