**Answer:**

Elia was riding of an hour from the house to the beach, of an hour from the beach to the house and rode

kilometers from the house to the beach and

kilometers from the beach to the house.

**Step-by-step explanation:**

1. Let b be the number of hours it took Elia to ride from her house to the beach, and p the number of hours it took her to ride from the beach to the park. The total duration of the rides was 1 hour, so

b + p = 1

2. Elia rode her bicycle from her house to the beach at a constant speed of 18 kilometers per hour, she was riding for b hour, then she rode 18b kilometers from her house to the beach.

Elia rode from the beach to the park at a constant speed of 15 kilometers per hour, she was riding for p hours, then she rode 15p kilometers from the beach to the house.

The distances she rode in each direction are equal, so

18b = 15p

3. Solve the system of two equations:

From the first equation

Substitute it into the second equation

Elia was riding of an hour from the house to the beach, of an hour from the beach to the house and rode

kilometers to the beach and

kilometers fro mthe beach to the house.