Answer:
Mi amiga es atlética.
Explanation:
In english, this means, "My friend is athletic."
La is the definite article for feminine nouns. Ex: La Fruta: The Fruit (Note: la and fruta both end in "a". That's how you know it's a feminine noun.)
For El it is the definite article for masculine nouns. Ex: El Libro: The Book (Note: for el, nouns end in "o")
Just to let you, you asked your math question in the Spanish section
This means " You know the whole city in one day "