You are following PEMDAS: (this is the order you use to solve a problem)
Parentheses, Exponents, Multiplication, Division, Addition, Subtraction
So you first simplify inside the parentheses, then you distribute/multiply 8 into the simplified values in the parentheses.
Also it would be easier to work with if you combined the like terms/simplified, because you still have to add them anyways if you didn't combine them earlier
