Can a person actually tap into the other 90% brain power and if so, how,how muc a nature vs nurture question?

I was wondering if an average person, better yet, can a mentally challenged person,if he/she is truly determined to and actually dedicates him/herself to develop his/her mind to the fullest? I mean, I know about the flowers for Algernon story, wouldn't it be great if each of us can tap into the other 90% of our brain power like Einstein did? I also know it's up to the individual person's wishes, inspirations, attitudes, outlook, desires, ambitions, how a person deals with his/her past failures and successes, etc., steadfast, unwavering dermination to succeed and do whatever it takes to improve him/herself, but is this lofty and noble goal really realistic today with all its distractions and responsibilities? But, really, who has the time and how much energy would a person need to have in order to reach or uplift his mental capacities? Or does that depends on which level of mental capacities that a person is at now. Or does it depend on having a really good teacher, mentor, etc? Obviously, money and the environment plays a big part, but if a person does not have either, how is a person supposed to go about it, if that is what a person does, indeed, really would like to achieve such as reading doing some of the things and exercises in Thought-Force in Business and Everyday Life by William, Walker Atkinson, Think and Grow Rich, may be some melvin Powers Clasic books, NLP books, etc,. And lastly, if a person wans;t really born with a great mind, does a person have to continuously practice to develop his/her mind? Thank you

Can a person actually tap into the other 90% brain power and if so, how,how muc a nature vs nurture question?
That humans only use 10% of their brain power is only a myth. A person can learn to think on a higher level but only though practice. Practice however can only do so much, some people are born with extraordinary minds and others are born with below average mental facilities. In the end, as with most things the single most important factor is determination. This being the case remember that there is no 90% waiting to be unlocked, only further refinement of what you already possess. You are not going to become a world class biologist if you weren't born one but that doesn't mean that you can't become more successful than someone who was.