What about opposite angles and sides of a parallelogram?

Let a parallelogram ABCD be given.

Pairs of sides AB and CD, AD and BC are parallel to each other and equal to each other.

Pairs of angles ∠A and ∠C, ∠B and ∠D are equal to each other.

The pairs of angles ∠A and ∠B, ∠B and ∠C, ∠C and ∠D, ∠A and ∠D add up to 180 °, since they are one-sided angles formed at the intersection of two parallel secant lines.

One of the components of a person's success in our time is receiving modern high-quality education, mastering the knowledge, skills and abilities necessary for life in society. A person today needs to study almost all his life, mastering everything new and new, acquiring the necessary professional qualities.