To solve the ratio \( \frac{x}{8} = \frac{y}{16} \) given that \( y = 3 \), we can substitute the value of \( y \) into the equation and solve for \( x \).
Substituting \( y = 3 \):
\[ \frac{x}{8} = \frac{3}{16} \]
Now, to find \( x \), we can cross-multiply:
\[ x \cdot 16 = 3 \cdot 8 \]
This simplifies to:
\[ 16x = 24 \]
Now, divide both sides by 16:
\[ x = \frac{24}{16} = \frac{3}{2} = 1.5 \]
So, the value of \( x \) is 1.5 units.