Hi there!
A remote interior angle is an angle that is located inside a triangle and at the opposite side of another angle. Therefore, every exterior angle has two remote interior angles.
The question asks for the remote interior angles of <1. First we must realise that the angle we're looking for is located inside the triangle. Our possibilities are <3, <4 and <5. Moreover, the angle must be at the opposite side of the exterior angle, and thus <5 isn't a remote interior angle.
The two remote interior angles of <1 are <3 and <4.