This is taken from the Miller Analogies Test. No explanation or context is given. My assumption is that the underscore stands for the same operation/number/whatever in both, but I don't know what it would be.
_23 : 1.5 :: _ 12 : 0.5
_05 : _05 :: 0 : Undefined
Sorry about using homework as the only tag, but I don't where else it would fit...?
Given $23$, we have $2$ into $3$ is $3/2=1.5$
Given $12$, we have $2$ into $1$ is $1/2=0.5$
Given $05$, we have $5$ into $0$ is $0/5=0$
However, $0$ into $5$ is $5/0$ which is undefined.
The pattern is...