Is the prayer valid for a 87-year-old grandmother who does not know how to pray, as she only recites part of Surat Al-Fatihah and part of the Greetings (Tashahhud)?

If an elderly woman does not know how to pray, and recites Al-Fatihah and Al-Tashahhud incompletely, she must learn what makes her prayer valid. This includes completing Al-Fatihah and Al-Tashahhud, as they are two pillars —according to the preponderant opinion— due to the Prophet's (peace be upon him) saying: "There is no prayer for one who does not recite the Opening of the Book." If she is able to learn and neglects to do so, she must make up the prayers she missed. However, if her inability to learn is genuine, then she must recite what she has memorized of Al-Fatihah and Al-Tashahhud. Whoever is unable to recite part of Al-Fatihah must recite the remainder. Some scholars have obligated reciting a substitute for what was not memorized from it, either from the Qur'an or by Dhikr (remembrance of Allah). If she has not memorized anything, she should repeat what she has memorized of Al-Fatihah. If she cannot recite anything at all, she should stand for the duration of reciting Al-Fatihah.