(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。
((5+6)+(6-7))=10
((5+6)-(7-6))=10
((5-7)+(6+6))=10
((6+(5+6))-7)=10
((6+6)+(5-7))=10
((6+6)-(7-5))=10
((6-7)+(5+6))=10
(5+((6+6)-7))=10
(5+(6+(6-7)))=10
(5+(6-(7-6)))=10
(5-((7-6)-6))=10
(5-(7-(6+6)))=10
(6+((5+6)-7))=10
(6+(5+(6-7)))=10
(6+(5-(7-6)))=10
(6+(6+(5-7)))=10
(6+(6-(7-5)))=10
(6-((7-5)-6))=10
(6-((7-6)-5))=10
(6-(7-(5+6)))=10