Answer:
square with sides of 6 in
Explanation:
Tessellation is the arrangement of shapes in repeated patterns without gaps or overlapping.
Tessellation is usually done with regular polygons. Only three regular shapes can tessellate, these are equilateral triangle, regular square and regular hexagon. For other polygon to tessellate, more than one shape must be used. A octagon can be used to make tessellations if it is used together with a square.
Mark uses tiles with shape of octagon of sides 6 in. To fill the gaps, Mark have to uses a square with sides of 6 in