One way to make addition easier is to use addition facts that we already know.
Let us try to find by first making 10.
We need to add 3 more to 7 to make 10. So move 3 green squares over.
Now we have the same number of squares, but there are 10 in the first ten-frame, and 5 in the second.
So is the same as which makes 15.
Now you have a go. What is ?