Or mine means that itself and 1 can only go into it. Conposit means that multiple numbers can go into it like 24. 12,6,8,2 can all go into it
We need to start from the innermost parenthesis and work our way out.
The first parenthesis is 
. These are not like terms because one involves a variable, while the other is a constant term. Two terms are summable if they involve the same power(s) of the same variable(s).
So, we can take one step outwards, and we arrive to the square brackets. We have
and 2z and -13z are like terms, so we can sum them:
Finally we arrive to the whole expression, which is
Because, again, 5z and 11z were like terms.
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Maybe you should contact your teacher
The answer is 3n-4 because 4 is being subtracted
