One child in black is walking down a hill covered in white snow while 2 children are on their knees.
There are three children in this picture, and they are all outside.
If the three children are on a hill covered in white snow that indicates that they are outside
One child in black and  2 children are on their knees.is inferred as three children.walking down a hill is inferred as outside.
One child and 2 children make three children total. If they are walking down a hill covered in snow, then they must be outside.