Learn Arabic (Modern Standard): في الحديقة ثلاثون شجرة وأربعون زهرة. - There are thirty trees and forty flowers in the garden.

In Arabic, the rules for counting change depending on the number. For numbers from 11 to 99, the item being counted must always be singular! So, instead of using the plural for trees, Arabic literally says "thirty tree" (ثلاثون شجرة).

Why do شجرة and زهرة have an "-an" sound (double fatha) at the end?

This is another special rule for counting with numbers 11 through 99. The singular noun that follows the number must be in the accusative case. For these words, that means adding a double fatha ending to make them "shajaratan" and "zahratan".

Where is the word for "there are" in this sentence?

Arabic doesn't use a specific word for "there are" in sentences like this. Instead, when a sentence starts with a prepositional phrase like في الحديقة (in the garden), it naturally creates the meaning of "There is..." or "There are..." in that place.

Why do the words for thirty and forty end in ـون (-uuna) instead of ـين (-iina)?

The "tens" numbers (20, 30, 40, etc.) change their endings depending on their role in the sentence, just like regular plural nouns. They use ـون when they are the subject, and ـين when they are the object or follow a preposition. Since "thirty" and "forty" are the subjects here (they are the things existing in the garden), they take the ـون ending.