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...?