To solve the ratio \( \frac{x}{8} = \frac{y}{16} \) with the new value of \( y = 3 \), we substitute \( y \) into the equation:
\[ \frac{x}{8} = \frac{3}{16} \]
Next, we can cross-multiply to solve for \( x \):
\[ 16x = 3 \times 8 \]
Calculating \( 3 \times 8 \):
\[ 16x = 24 \]
Now, divide both sides by 16:
\[ x = \frac{24}{16} \]
This simplifies to:
\[ x = \frac{3}{2} \text{ or } 1.5 \text{ units} \]
So, the correct answer is:
1.5 units.