Learn Hardcore Norwegian: Hun trenger bruksenhetsnummeret uavhengig av om hun bor alene. - She needs the unit number regardless of whether she lives alone.

In this sentence, Norwegian needs the subject to be stated, so you cannot normally leave out hun. Standard Norwegian usually requires an explicit subject:

Hun trenger ... = She needs ...

Unlike in English, Norwegian also uses det or other dummy subjects in many places where needed, so subject omission is generally not a feature of normal sentence structure.

Why is it trenger and not something like trenge?

Trenger is the present tense of the verb å trenge (to need).

So:

å trenge = to need
trenger = need / needs

In Norwegian, the present tense is often formed with -er:

jeg trenger = I need
hun trenger = she needs

Unlike English, the verb does not change depending on the subject. So both jeg trenger and hun trenger use the same verb form.

What is bruksenhetsnummeret, and why is it one long word?