26-{31-[29-(57+31)]}

26 - {31 - [29 - (57 + 31)]} = = 26 - {31 - (29 - 88)} = = 26 - {31 - (-59)} = = 26 - (31 + 59) = = 26 - 90 = = -64

26-(31-(29-(57+31)))=26-(31-(29-88))=26-(31-(-51))=26-(31+51)=26-82=-56  :)