You have the following algebraic expression:
16 + (f + 4)
In order to simplify the previous expression you proceed as follow:
Eliminate parenthesis, in this case it is not ne cessary to change the signs of the terms inside parenthesis becasue the sign before the parenthesis is +. Then, you have:
16 + (f + 4) = 16 + f + 4
order the terms in such a way you have like terms together:
16 + f + 4 = 16 + 4 + f
simplify like terms, in this you hvae 16 and 4 as like terms because they are independent coefficients:
16 + 4 + f = 20 + f
Hence, the simplified expression to the given expression is
20 + f