Adele, Dennis, and Marie are siblings.
The sum of their ages is 30. Marie is the
eldest, and Adele is the youngest. None of
the siblings are older than 15 or younger
than 5. No two are the same age. List all
the combinations of ages they could be.

Step-by-step explanation:

Let Adele's age be represented by x, Dennis age by y and Marie's age by z. Since the sum of their age is 30, then:

              x + y + z = 30      1

Given the conditions that:

a. Marie is the eldest and Adele is the youngest.

b. None of the siblings is older than 15 or younger than 5.

c. No two have the same age.

From equation 1, some of the possible combinations of their ages are:

i.        5 + 10 + 15 = 30

ii.       5 + 11 + 14 = 30

iii.      5 + 13 + 12 = 30

iii.      7 + 8 + 15 = 30

iv.      7 + 9 + 14 = 30

v.       7 + 10 + 13 = 30

vi.      9 + 10 + 11 = 30

vii.     7 + 11 + 12 = 30

viii.    6 + 9 + 15 = 30

ix.      6 + 10 + 14 = 30

x.       8 + 9 + 13 = 30