Chapter 2 - Solving Equations - 2-3 Solving Multi-Step Equations - Practice and Problem-Solving Exercises - Page 98: 23

$z=3.75$

Start with the given equation: $5(2+4z)=85$ We use the distributive property to expand the left side of the equation: $10+20z=85$ We subtract $10$ from both sides of the equation: $20z=85-10$ We combine like terms: $20z=75$ We divide both sides of the equation by $20$: $z=\frac{75}{20}=3.75$