This particular problem is attributed to Alcuin. The wording does not give sufficient information to answer the question without making legal assumptions. Please share your assumptions with your solution.
A dying man left 960 shillings and a pregnant wife. He directed that if a boy was born, he should receive three-quarters of the whole and the child's mother should receive one-quarter. But if a daughter was born, she would receive seven-twelfths, and her mother five-twelfths. It happened however that twins were born - a boy and a girl. How much should the mother receive, how much the son, and how much the daughter?
https://www.maa.org/press/periodicals/convergence/using-historical-problems-in-the-middle-school-a-problem-from-alcuin-of-york
The above article lists many possible approaches with distinct results.
I would like to add another variant of possible assumption: depends who of the twins was delivered first:
Case 1 �"boy gets 3/4 , mother & girl divide rhe remaining 5:7 i.e. 5/48 mother and 7/48 girl
Case 2 �"girl gets 7/12 , mother & boy divide the remaining 1:3 - mother 5/48 boy 5/16
Edited on July 25, 2017, 1:18 pm