ANSWER
[tex]?=13z[/tex]EXPLANATION
We want to find the missing term on the right-hand side of the equation:
[tex]5z-3+8z+7=\text{?}+4[/tex]To do this, we simply have to simplify the left-hand side of the equation and compare it to the right-hand side.
That is:
[tex]\begin{gathered} 5z-3+8z+7 \\ 5z+8z-3+7 \\ 13z+4 \end{gathered}[/tex]Comparing this to the right-hand side, we see that:
[tex]?=13z[/tex]