So Mohammad did not marry a 9 year old? Is that your claim?
Well, if you believe that, I'm assuming you believe that everything in Bukhari's hadith collection is true. That's the origin of that claim. So, are you Sunni or Shi'ah?
Her age was lowered in that report so that no questions would be raised about her virginity, and by extension, the legitimacy of Muhammad's offspring through her.
Source: "All of these specific references to the bride's age reinforce Aisha's pre-menarcheal status and, implicitly, her virginity. They also suggest the variability of Aisha's age in the historical record." - D. A. Spellberg, Politics, Gender, and the Islamic Past.
In reality, she had been betrothed to Jubair Ibn al Mut'am, a pagan, before her engagement to Muhammad. Jubair eventually annulled their engagement. In at least two separate sources it is pointed out that Asma bint Abi Bakr, Aisha's half-sister, was 100 years old when she died in 73 AH. That would make Aisha 90 in 73 AH.
Source: "Asma died in 73 A.H. at the age of one hundred years. She was ten years older than her sister Aisha." - Ibn Kathir, Al-bidayya wal-nihaya
"She was the sister of Aisha Siddiqa, wife of the Holy Prophet, and was ten years older than her. Â… In 73 A.H. Â… Asma died at the age of one hundred years." - Mishkat al-Masabih
Aisha's marriage to Muhammad took place in the year of the Hijra, 1 AH or 622 AD. You do the math...