To solve the equation \( x8 = y16 \) for \( x \) when \( y = 3 \), we can start by rewriting the equation in a more workable form by isolating \( x \):
Given the ratio:
\[ \frac{x}{8} = \frac{y}{16} \]
Now substituting \( y = 3 \):
\[ \frac{x}{8} = \frac{3}{16} \]
Now we can cross-multiply to solve for \( x \):
\[ 16x = 3 \times 8 \]
Calculating the right side:
\[ 16x = 24 \]
Now divide both sides by 16:
\[ x = \frac{24}{16} = \frac{3}{2} = 1.5 \]
Thus, the value of \( x \) is 1.5 units.