Is the method of calculating inheritance for a father, mother, and full sister correct?

If the deceased leaves behind only a mother, a father, and a full sister, then the mother receives one-third as a prescribed share due to the absence of a descendant heir and multiple siblings, based on the Almighty's saying: "And if he had no child and his parents inherited him, then for his mother is one-third." The remainder goes to the father by way of ta'sib (residuary heir), based on the Prophet's (peace be upon him) saying: "Give the prescribed shares to those entitled to them, and what remains is for the closest male relative." The full sister receives nothing because she is entirely excluded by the father.

Thus, the inheritance is divided into three shares: one share for the mother and two shares for the father.

It should be noted that matters of inheritance are critical and complex, and a mere fatwa is insufficient. Rather, the matter must be presented to a Sharia court for examination and investigation, as there might be another heir, or wills, or debts that take precedence over the rights of the heirs.