Smite Skill: Scales of Fate

Not in this case- it's impossible to simplify a "formula" with 2 different, independant variables like that; she doesn't increase her power by the amount that she reduced on the enemy, but based on her personal physical power. The more you have, the more you get. Similarly, the more power they have, the more you reduce.

So if you wanted to represent the amount of power (which changes somehow) provided by the passive (based on the both gods' combined power level, that's what you wanted to achieve from what I've understood) it'd simply be:

0.24X + 0.24Y

where X is target's power and Y is your power (or the other way round, doesn't make any difference)- the result will be a "flat", and not percentage amount.

kind-of-edit:
Oh at the end I realised that there's one word which might've caused the confusion: power "steal"- in-game it is stated correctly: power gain & power loss. In a sense it could be treated as a steal mechanic as with every hit your power increases at someone's cost, but technically they're both independant values.