If two figures are similar, their angles are congruent and their sides are proportional.

Congruent angles have the same measure and if two figures are similar, each angle in one figure has a corresponding angle with the same measure in the other figure.

Proportional sides means that if two corresponding sides are divided, their quotient are equal to the quotient of two other corresponding sides. $$\frac{1.8}{1.3}=\frac{2.7}{2}=\frac{3.5}{2.6}=1.35$$