3:6=х:8

To solve the proportion \( \frac{3}{6} = \frac{x}{8} \), you can cross-multiply:

1. Cross-multiply: \[ 3 \cdot 8 = 6 \cdot x \]

2. Simplify the left side: \[ 24 = 6x \]

3. Now, to isolate \( x \), divide both sides by 6: \[ x = \frac{24}{6} = 4 \]

So, \( x = 4 \).