Remove parentheses.

Subtract from .

Add and .

Subtract from .

Add and .

Subtract from .

Add and .

Subtract from .

Add and .

Subtract from .

Add and .

Subtract from .

Raise to the power of .

Divide by .

Evaluate ((1-8.7+(9-8.7)+(4-8.7)+(12-8.7)+(13-8.7)+(13-8.7))^2)/6