-2(x-3y)-3x+5y)-(6x-8y)

Answer 1

I see mismatched brackets ...

is it
-2(x-3y)-3(x+5y)-(6x-8y)
or
-2(x-3y)-(3x+5y)-(6x-8y)
or
....

(the brackets going left must have the same count as the brackets to the right)

Answer 2

if -2(x-3y)-3(x+5y)-(6x-8y)
then
= -2x + 6y - 3x - 15y - 6x + 8y
= -11x - y

if -2(x-3y)-(3x+5y)-(6x-8y) .
then
= -2x + 6y - 3x - 5y - 6x + 8y
= -11x + 9y