How many line(s) of symmetry does Fig. 1.3 have?

The markings on the sides of Fig. 1.3 (double dashes on all three sides) indicate that all three sides of the triangle are equal in length. This means the triangle is an equilateral triangle.

An equilateral triangle has three lines of symmetry. Each line of symmetry passes through a vertex and the midpoint of the opposite side.

Fig. 1.3 has $\boxed{\text{3}}$ line(s) of symmetry.