Qur'anic verses - Case 3:

A woman died leaving a husband, a son, a duaghter and parents:

(1) The inheritance is divided into equal shares:

no. of shares, say = 12 x (2 x S + D)

(where, S = no. of sons; D = no. of daughters)

in this case,
12 x (2 x 1 + 1) = 36 shares

(2) The husband, according to verse (4:12), inherits quarter of the whole inheritance:

husband's shares = 1/4 x 36 = 9

(3) Each parent, according to verse (4:11), inherits one sixth of the whole inheritance:

each parent's shares = 1/6 x 36 = 6

For parents, a sixth share of the inheritance to each, if the deceased left children.
[Qur'an 4:11]

(4) The remaining inheritance is divided between the children in accordance with verse (4:11), such that the male takes twice the share of a female:

(remaining = 36 - 6 - 6 - 9 = 15 shares)

daughter = 15 / (2 x S + D) = 15 / 3 = 5 shares

son = 5 x 2 = 10 shares

God (thus) directs you as regards your Children's (Inheritance): to the male, a portion equal to that of two females.
[Qur'an 4:11]