Bert has 10 books and he wants to give Bert has 10 books and he wants to give 2 of these books to his sister. How many different gifts are possible?

“exterior angles of triangles. an exterior (or external) angle is the angle between one side of a triangle and the extension of an adjacent side. try this drag the orange dots on any vertex to reshape the triangle.” look to get to the answer i explained what it means and other things i hope it you .