5/1:?/8

To solve the proportion \( \frac{5}{1} = \frac{x}{8} \), we can use cross multiplication.

Cross multiplying gives us:

\[ 5 \cdot 8 = 1 \cdot x \] \[ 40 = x \]

Thus, \( x = 40 \).

Therefore, the complete proportion is \( \frac{5}{1} = \frac{40}{8} \).