I am in a finite mathematics class and have been given the following Pr[A|B] = 3/4 Pr[B|A] = 3/8 and Pr[A u B] = 1

I have been asked to find Pr[A] Pr[B] and Pr[A n B]

the book has provided the formula:

Pr[A|B] =Pr[A n B]Pr[B|A] =Pr[B n A]

Pr[B] Pr[A]

I am having difficulty understanding where to begin with this. Thanks.