Question

Question #d8b61

Answer 1

Patricia - this is a combination problem since the order of the ornaments does not matter.

Explanation:

There is a duck at each end of the 10 item row:

DxxxxxxxxxD

Now, no more ducks can be used ... only shells and wooden animals.

There are 8 empty spots and we have 10 items (4 shells and 6 wooden animals) to choose from:

`""_10C_8= (10!)/(2!8!) = 45` arrangements.

Hope that helped