relationship Equity-Price-Earning growth rate

Hi! i was reviewing some theoretical financial modelling stuff and i came up with a question i hope you will be so kind to answer:

how can i come up with the implied earnings growth necessary to justify the current price given there are no more equity offerings and no buybacks?

that is, i have my equity, to which i add my earnings (say there is no aggressive accounting [like autonomy and the recent 8,8bn writeoff] => sustainable) and i want to come up with the implied earnings growth necessary to justify the current price. take everything else equal (which is not in reality but once i get a model i will make it more complex if possible)

thanks!