Answer:
7
Explanation:
Regular polygons have the same number of lines of symmetry as they do sides.
Polygons with an even number of sides have a line of symmetry for each pair of opposite vertices, as well as a line of symmetry through midpoints of opposite sides.
Polygons with an odd number of sides have a line of symmetry for each vertex, passing through the midpoint of the opposite side.
A heptagon has 7 vertices, and therefore has 7 lines of symmetry.