Julia saw ten birds sitting on a branch of a tree. She saw five more birds in a nest on top of the tree. Seven of the birds flew off the branch. How many birds were left on the tree?
10   8   9   7

Total birds sitting on the tree = 10 + 5 = 15 birds. Out of these, 7 flew away. Therefore, birds left on the tree = 15 - 7 = 8 birds. That is how I got my answer that is this time see you later.