You can use 2 shapes, but you can't have any overlap or gap.
Think about what you know for tessellations:
I know a shape tessellates if it's angles are factors of 360.
Observations
*When I look at their vertices (where the shapes come together) it equals 360.
*Angle measure is always 360 (with no overlaps or gaps)
*Can draw triangles in hexagon. 60+60=120
*I can tell they tile if the angle measures added together equal 360.
*The shapes make the angle for the other shape.