The pronunciation of the Spanish letter RR can be difficult for students. It is the same sound as the single R, but twice as long.
Note that when R is at the beginning of a word, it is pronounced like RR.
In Spanish, RR is considered a single letter. It's very important to be aware of this when looking something up in a Spanish dictionary. When words have RR in the middle, they will be after words with R + any other letter. For example, carro is located after cartel.