Dverview 1 2 3 8 9 10 11 12 Question Progress $1 / 3$ Marks Homework Progress $18 / 39$ Marks In a group of 30 people, 12 have a sister 15 have a brother 11 do not have a sister nor a brother Complete the Venn diagram to show this information. $\xi=$ group of 30 people. $\mathrm{S}=$ people who have a sister. $B=$ people who have a brother.

Step 1 ：Let A be the number of people who have both a sister and a brother, S_only be the number of people who have only a sister, and B_only be the number of people who have only a brother.

Step 2 ：We know that \(A + S_{only} = 12\), \(A + B_{only} = 15\), and \(A + S_{only} + B_{only} + 11 = 30\).

Step 3 ：Solving these equations, we find that \(A = 8\), \(S_{only} = 4\), and \(B_{only} = 7\).

Step 4 ：\(\boxed{8}\) people have both a sister and a brother, \(\boxed{4}\) people have only a sister, \(\boxed{7}\) people have only a brother, and \(\boxed{11}\) people have neither a sister nor a brother.