3,负五,7,负十二凑24点.

(7-(-5))*3-12=24
((7-(-5))*3)-12=24
(-5)-7+3*12=24
((-5)-7)+3*12=24
(-5)-7+(3*12)=24
((-5)-7)+(3*12)=24
(-5)-(7-3*12)=24
(-5)-(7-(3*12))=24
(-5)-7+12*3=24
((-5)-7)+12*3=24
(-5)-7+(12*3)=24
((-5)-7)+(12*3)=24
(-5)-(7-12*3)=24
(-5)-(7-(12*3))=24
(-5)+3*12-7=24
(-5)+(3*12)-7=24
((-5)+3*12)-7=24
(-5)+(3*12-7)=24
((-5)+(3*12))-7=24
(-5)+((3*12)-7)=24
(-5)+12*3-7=24
(-5)+(12*3)-7=24
((-5)+12*3)-7=24
(-5)+(12*3-7)=24
((-5)+(12*3))-7=24
(-5)+((12*3)-7)=24
3*(7-(-5))-12=24
(3*(7-(-5)))-12=24
3*12-7+(-5)=24
(3*12)-7+(-5)=24
(3*12-7)+(-5)=24
((3*12)-7)+(-5)=24
3*12-(7-(-5))=24
(3*12)-(7-(-5))=24
3*12+(-5)-7=24
(3*12)+(-5)-7=24
3*12+((-5)-7)=24
(3*12+(-5))-7=24
(3*12)+((-5)-7)=24
((3*12)+(-5))-7=24
12*3-7+(-5)=24
(12*3)-7+(-5)=24
(12*3-7)+(-5)=24
((12*3)-7)+(-5)=24
12*3-(7-(-5))=24
(12*3)-(7-(-5))=24
12*3+(-5)-7=24
(12*3)+(-5)-7=24
12*3+((-5)-7)=24
(12*3+(-5))-7=24
(12*3)+((-5)-7)=24
((12*3)+(-5))-7=24