We are given the equation $\frac{c}{d} = \frac{b}{a}$ and asked to solve for $d$.

1. Problem Description

We are given the equation $\frac{c}{d} = \frac{b}{a}$ and asked to solve for $d$.

2. Solution Steps

We start with the given equation:

$\frac{c}{d} = \frac{b}{a}$

Multiply both sides by $d$:

$c = \frac{bd}{a}$

Multiply both sides by $a$:

$ac = bd$

Divide both sides by $b$:

$\frac{ac}{b} = d$

Thus we have solved for $d$.

3. Final Answer

$d = \frac{ac}{b}$