#### Answer

$\frac{1}{16}$

#### Work Step by Step

First, we rewrite the given ratio as a fraction: $\frac{0.5ab}{8ab}$
Next, we find a common factor that is in both the numerator and the denominator, and factor it out: $\frac{ab(0.5)}{ab(8)}$
When you divide any number by itself, you get $1$, so we can cancel out the common factor. This leaves us with $\frac{0.5}{8}=\frac{1}{16}$