Step 1: Identify lines of symmetry for each figure Step 2: Equilateral triangle: 3 lines (one through each vertex and midpoint of opposite side) Step 3: Isosceles triangle: 1 line (vertical, through the apex to the base midpoint) Step 4: Square: 4 lines (2 through midpoints of opposite sides, 2 through opposite corners) Step 5: Rectangle (unequal sides): 2 lines (vertical and horizontal through midpoints) Answer: Isosceles triangle has exactly 1 line of symmetry.