distribute the 5 to whats inside the parentheses
[tex]3z+10-5z=2z-10[/tex]simplify the common factors on both sides
[tex]-2z+10=2z-10[/tex]bring all algebraic expressions to one side, and to the other all constant numbers
[tex]-2z-2z=-10-10[/tex]simplify both sides
[tex]\begin{gathered} -4z=-20 \\ \end{gathered}[/tex]divide both sides by 4
[tex]\begin{gathered} z=\frac{-20}{-4} \\ z=5 \end{gathered}[/tex]