As Exxcentrica has said, there is no r with a tilde on top. But, if I am not confused, you are asking about the different pronunciation of the r in Spanish. You pronounce previo (and the r is soft) and carrera (double r much more strongly). The double r is never written at the beginning of a word, for instance, you say raro, the first r is stronger than the second one.
I hope it helps you.
|