# Use multiplying by 1 to find an expression equivalent to 17/9 with a denominator of 9d?

$\frac{17}{9} \cdot \frac{d}{d} \to 17 \frac{d}{9} d$
For the denominator of $9$ to transform to $9 d$ we must multiply by $d$. So, in order to keep the term $\frac{17}{9}$ at the same value but with a denominator of $9 d$ we must multiply by $1$ in the form of $\frac{d}{d}$:
$\frac{17}{9} \cdot \frac{d}{d} \to 17 \frac{d}{9} d$