It is given that y varies inversely as (2z+3) and that y = 1 when z = 1. (a) Express y in terms of z. (b) Find the value of z when y = 5.

Given that $y$ varies inversely as $(2x+3)$, we can write the relationship as:

$$y = \frac{k}{2x+3}$$

where $k$ is the constant of proportionality.

We are given that $y=1$ when $x=1$. Substitute these values into the equation:

$$1 = \frac{k}{2(1)+3}$$ $$1 = \frac{k}{2+3}$$ $$1 = \frac{k}{5}$$ $$k = 5$$

$$y = \frac{5}{2x+3}$$

The expression for $y$ in terms of $x$ is $\boxed{y = \frac{5}{2x+3}}$.

Divide both sides by 5:

$$\frac{5}{5} = \frac{1}{2x+3}$$ $$1 = \frac{1}{2x+3}$$

Multiply both sides by $(2x+3)$:

$$1 \times (2x+3) = 1$$ $$2x+3 = 1$$

Subtract 3 from both sides:

$$2x = 1-3$$ $$2x = -2$$

Divide by 2:

$$x = \frac{-2}{2}$$ $$x = -1$$

The value of $x$ when $y=5$ is $\boxed{-1}$.